Como posso criar uma API SOAP / XML-RPC v1 e V2 personalizada no magento?

Como posso criar uma API SOAP / XML-RPC V1 e V2 personalizada no Magento?

Você pode ler isso . Isso explica muito, mas é principalmente para a API V1.
Para mostrar como você pode criar uma API, acho melhor oferecer um exemplo.
Digamos que você tenha um módulo nomeado Easylife_Portfoliocom uma entidade nomeada Project.
Para esta entidade, você pode definir o nome, descrição e status.
Aqui estão os arquivos que você precisa, além do restante dos arquivos (controladores, modelos, blocos ...).
app/code/local/Easylife/Portfolio/etc/api.xml- o arquivo de declaração da API.

<?xml version="1.0"?>
<config>
    <api>
        <resources>
            <portfolio_project translate="title" module="portfolio">
                <title>Project API</title>
                <model>portfolio/project_api</model>
                <acl>portfolio/project</acl><!-- acl resource alias -->
                <methods><!-- definne the methods -->
                    <list translate="title" module="portfolio"><!-- list projects -->
                        <title>Retrieve list of projects</title>
                        <method>items</method>
                        <acl>portfolio/project/list</acl>
                    </list>
                    <info translate="title" module="portfolio"><!-- project details -->
                        <title>Retrieve project info</title>
                        <acl>portfolio/project/info</acl>
                    </info>
                    <add translate="title" module="portfolio"><!-- add project -->
                        <title>Add project</title>
                        <acl>portfolio/project/add</acl>
                    </add>
                    <update translate="title" module="portfolio"><!-- update project -->
                        <title>Update project</title>
                        <acl>portfolio/project/update</acl>
                    </update>
                    <remove translate="title" module="portfolio"><!-- remove project-->
                        <title>Remove project</title>
                        <acl>portfolio/project/remove</acl>
                    </remove>
                </methods>
                <faults module="portfolio"><!-- errors that might appear-->
                    <project_not_exists>
                        <code>101</code>
                        <message>Requested project does not exist.</message>
                    </project_not_exists>
                    <invalid_data>
                        <code>102</code>
                        <message>Provided data is invalid.</message>
                    </invalid_data>
                    <save_error>
                        <code>103</code>
                        <message>Error while saving project. Details in error message.</message>
                    </save_error>
                    <remove_error>
                        <code>104</code>
                        <message>Error while removing project. Details in error message.</message>
                    </remove_error>
                </faults>
            </portfolio_project>
        </resources>
        <resources_alias>
            <project>portfolio_project</project>
        </resources_alias>
        <v2>
            <resources_function_prefix>
                <project>portfolioProject</project>
            </resources_function_prefix>
        </v2>
        <acl><!-- acl definition -->
            <resources>
                <portfolio translate="title" module="portfolio">
                    <title>Portfolio</title>
                    <project translate="title" module="portfolio">
                        <title>Project</title>
                        <sort_order>110</sort_order>
                        <list translate="title" module="portfolio">
                            <title>List</title>
                        </list>
                        <info translate="title" module="portfolio">
                            <title>Info</title>
                        </info>
                        <add translate="title" module="portfolio">
                            <title>Add</title>
                        </add>
                        <update translate="title" module="portfolio">
                            <title>Update</title>
                        </update>
                        <remove translate="title" module="portfolio">
                            <title>Remove</title>
                        </remove>
                    </project>
                </portfolio>
            </resources>
        </acl>
    </api>
</config>

app/code/local/Easylife/Portfolio/etc/wsdl.xml - parte wsdl para V2

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns:typens="urn:{{var wsdl.name}}" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
    xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns="http://schemas.xmlsoap.org/wsdl/"
    name="{{var wsdl.name}}" targetNamespace="urn:{{var wsdl.name}}">
    <types>
        <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:Magento">
            <import namespace="http://schemas.xmlsoap.org/soap/encoding/" schemaLocation="http://schemas.xmlsoap.org/soap/encoding/" />
            <complexType name="portfolioProjectListEntity"><!-- define type for project list -->
                <all>
                    <element name="entity_id" type="xsd:string" minOccurs="1" />
                    <element name="name" type="xsd:string" minOccurs="1" />
                    <element name="description" type="xsd:string" minOccurs="0" />
                    <element name="status" type="xsd:string" minOccurs="0" />
                    <element name="created_at" type="xsd:string" minOccurs="1" />
                    <element name="updated_at" type="xsd:string" minOccurs="1" />
                </all>
            </complexType>
            <complexType name="portfolioProjectListEntityArray"><!-- define type array of projects -->
                <complexContent>
                    <restriction base="soapenc:Array">
                        <attribute ref="soapenc:arrayType" wsdl:arrayType="typens:portfolioProjectListEntity[]" />
                    </restriction>
                </complexContent>
            </complexType>
            <complexType name="portfolioProjectAddEntity"><!-- define type for add project -->
                <all>
                    <element name="name" type="xsd:string" minOccurs="1" />
                    <element name="description" type="xsd:string" minOccurs="0" />
                    <element name="status" type="xsd:string" minOccurs="0" />

                </all>
            </complexType>
            <complexType name="portfolioProjectUpdateEntity"><!-- define type for update project -->
                <all>
                    <element name="name" type="xsd:string" minOccurs="1" />
                    <element name="description" type="xsd:string" minOccurs="0" />
                    <element name="status" type="xsd:string" minOccurs="0" />

                </all>
            </complexType>
            <complexType name="portfolioProjectInfoEntity"><!-- define type for retrieve info -->
                <all>
                    <element name="entity_id" type="xsd:string" minOccurs="1" />
                    <element name="name" type="xsd:string" minOccurs="1" />
                    <element name="description" type="xsd:string" minOccurs="0" />
                    <element name="status" type="xsd:string" minOccurs="0" />

                    <element name="created_at" type="xsd:string" minOccurs="1" />
                    <element name="updated_at" type="xsd:string" minOccurs="1" />
                </all>
            </complexType>
                </schema>
    </types>
    <!--[+] define messages -->
    <message name="portfolioProjectListRequest">
        <part name="sessionId" type="xsd:string" />
        <part name="filters" type="typens:filters"/>
    </message>
    <message name="portfolioProjectListResponse">
        <part name="result" type="typens:portfolioProjectListEntityArray" />
    </message>
    <message name="portfolioProjectInfoRequest">
        <part name="sessionId" type="xsd:string" />
        <part name="projectId" type="xsd:string" />
    </message>
    <message name="portfolioProjectInfoResponse">
        <part name="result" type="typens:portfolioProjectInfoEntity" />
    </message>
    <message name="portfolioProjectAddRequest">
        <part name="sessionId" type="xsd:string" />
        <part name="data" type="typens:portfolioProjectAddEntity" />
    </message>
    <message name="portfolioProjectAddResponse">
        <part name="result" type="xsd:int"/>
    </message>
    <message name="portfolioProjectUpdateRequest">
        <part name="sessionId" type="xsd:string" />
        <part name="projectId" type="xsd:string" />
        <part name="data" type="typens:portfolioProjectUpdateEntity" />
    </message>
    <message name="portfolioProjectUpdateResponse">
        <part name="result" type="xsd:boolean" />
    </message>
    <message name="portfolioProjectRemoveRequest">
        <part name="sessionId" type="xsd:string" />
        <part name="projectId" type="xsd:string" />
    </message>
    <message name="portfolioProjectRemoveResponse">
        <part name="result" type="xsd:boolean" />
    </message>
    <!--[-] define messages -->
    <!--[+] define portTypes -->
    <portType name="{{var wsdl.handler}}PortType">
        <operation name="portfolioProjectList">
            <documentation>Retrieve list of project</documentation>
            <input message="typens:portfolioProjectListRequest" />
            <output message="typens:portfolioProjectListResponse" />
        </operation>
        <operation name="portfolioProjectInfo">
            <documentation>Retrieve project info</documentation>
            <input message="typens:portfolioProjectInfoRequest" />
            <output message="typens:portfolioProjectInfoResponse" />
        </operation>
        <operation name="portfolioProjectAdd">
            <documentation>Add project</documentation>
            <input message="typens:portfolioProjectAddRequest" />
            <output message="typens:portfolioProjectAddResponse" />
        </operation>
        <operation name="portfolioProjectUpdate">
            <documentation>Update project</documentation>
            <input message="typens:portfolioProjectUpdateRequest" />
            <output message="typens:portfolioProjectUpdateResponse" />
        </operation>
        <operation name="portfolioProjectRemove">
            <documentation>Remove project</documentation>
            <input message="typens:portfolioProjectRemoveRequest" />
            <output message="typens:portfolioProjectRemoveResponse" />
        </operation>
    </portType>
    <!--[-] define portTypes -->
    <!--[+] define binding -->
    <binding name="{{var wsdl.handler}}Binding" type="typens:{{var wsdl.handler}}PortType">
        <soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http" />
        <operation name="portfolioProjectList">
            <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
            <input>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </input>
            <output>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </output>
        </operation>
        <operation name="portfolioProjectInfo">
            <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
            <input>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </input>
            <output>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </output>
        </operation>
        <operation name="portfolioProjectAdd">
            <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
            <input>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </input>
            <output>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </output>
        </operation>
        <operation name="portfolioProjectUpdate">
            <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
            <input>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </input>
            <output>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </output>
        </operation>
        <operation name="portfolioProjectRemove">
            <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
            <input>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </input>
            <output>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </output>
        </operation>
    </binding>
    <!--[-] define portTypes -->
    <service name="{{var wsdl.name}}Service">
        <port name="{{var wsdl.handler}}Port" binding="typens:{{var wsdl.handler}}Binding">
            <soap:address location="{{var wsdl.url}}" />
        </port>
    </service>
</definitions>

app/code/local/Easylife/Portfolio/etc/wsi.xml- é semelhante, wsdl.xmlmas é usado para conformidade com WS-I

<?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions xmlns:typens="urn:{{var wsdl.name}}"
     xmlns:xsd="http://www.w3.org/2001/XMLSchema"
     xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
     xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
     xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
     name="{{var wsdl.name}}"
     targetNamespace="urn:{{var wsdl.name}}">
    <wsdl:types>
        <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:{{var wsdl.name}}">
            <xsd:complexType name="portfolioProjectListEntityArray">
                <xsd:sequence>
                    <xsd:element maxOccurs="unbounded" name="complexObjectArray" type="typens:portfolioProjectListEntity" />
                </xsd:sequence>
            </xsd:complexType>
            <xsd:complexType name="portfolioProjectListEntity">
                <xsd:sequence>
                    <xsd:element name="entity_id" type="xsd:string" />
                    <xsd:element name="name" type="xsd:string" />
                    <xsd:element name="description" type="xsd:string" />
                    <xsd:element name="status" type="xsd:string" />

                    <xsd:element name="created_at" type="xsd:string" />
                    <xsd:element name="updated_at" type="xsd:string" />
                </xsd:sequence>
            </xsd:complexType>
            <xsd:complexType name="portfolioProjectAddEntity">
                <xsd:sequence>
                    <xsd:element name="name" type="xsd:string" />
                    <xsd:element name="description" type="xsd:string" />
                    <xsd:element name="status" type="xsd:string" />

                </xsd:sequence>
            </xsd:complexType>
            <xsd:complexType name="portfolioProjectUpdateEntity">
                <xsd:sequence>
                    <xsd:element name="name" type="xsd:string" />
                    <xsd:element name="description" type="xsd:string" />
                    <xsd:element name="status" type="xsd:string" />

                </xsd:sequence>
            </xsd:complexType>
            <xsd:complexType name="portfolioProjectInfoEntity">
                <xsd:sequence>
                    <xsd:element name="entity_id" type="xsd:string" />
                    <xsd:element name="name" type="xsd:string" />
                    <xsd:element name="description" type="xsd:string" />
                    <xsd:element name="status" type="xsd:string" />

                    <xsd:element name="created_at" type="xsd:string" />
                    <xsd:element name="updated_at" type="xsd:string" />
                </xsd:sequence>
            </xsd:complexType>

            <xsd:element name="portfolioProjectListRequestParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
                        <xsd:element minOccurs="0" maxOccurs="1" name="filters" type="typens:filters" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectListResponseParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="result" type="typens:portfolioProjectListEntityArray" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectInfoRequestParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
                        <xsd:element minOccurs="1" maxOccurs="1" name="projectId" type="xsd:string" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectInfoResponseParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="result" type="typens:portfolioProjectInfoEntity" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectAddRequestParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
                        <xsd:element minOccurs="1" maxOccurs="1" name="data" type="typens:portfolioProjectAddEntity" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectAddResponseParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="result" type="xsd:int" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectUpdateRequestParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
                        <xsd:element minOccurs="1" maxOccurs="1" name="projectId" type="xsd:string" />
                        <xsd:element minOccurs="1" maxOccurs="1" name="data" type="typens:portfolioProjectUpdateEntity" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectUpdateResponseParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="result" type="xsd:boolean" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectRemoveRequestParam">
                <xsd:complexType>
                    <xsd:sequence>
                    <xsd:element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
                        <xsd:element minOccurs="1" maxOccurs="1" name="projectId" type="xsd:string" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
            <xsd:element name="portfolioProjectRemoveResponseParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="result" type="xsd:boolean" />
                    </xsd:sequence>
                 </xsd:complexType>
            </xsd:element>
                </xsd:schema>
    </wsdl:types>
    <wsdl:message name="portfolioProjectListRequest">
        <wsdl:part name="parameters" element="typens:portfolioProjectListRequestParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectListResponse">
        <wsdl:part name="parameters" element="typens:portfolioProjectListResponseParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectInfoRequest">
        <wsdl:part name="parameters" element="typens:portfolioProjectInfoRequestParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectInfoResponse">
        <wsdl:part name="parameters" element="typens:portfolioProjectInfoResponseParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectAddRequest">
        <wsdl:part name="parameters" element="typens:portfolioProjectAddRequestParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectAddResponse">
        <wsdl:part name="parameters" element="typens:portfolioProjectAddResponseParam"/>
    </wsdl:message>
    <wsdl:message name="portfolioProjectUpdateRequest">
        <wsdl:part name="parameters" element="typens:portfolioProjectUpdateRequestParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectUpdateResponse">
        <wsdl:part name="parameters" element="typens:portfolioProjectUpdateResponseParam"/>
    </wsdl:message>
    <wsdl:message name="portfolioProjectRemoveRequest">
        <wsdl:part name="parameters" element="typens:portfolioProjectRemoveRequestParam" />
    </wsdl:message>
    <wsdl:message name="portfolioProjectRemoveResponse">
        <wsdl:part name="parameters" element="typens:portfolioProjectRemoveResponseParam" />
    </wsdl:message>
    <wsdl:portType name="{{var wsdl.handler}}PortType">
        <wsdl:operation name="portfolioProjectList">
            <wsdl:documentation>Retrieve list of projects</wsdl:documentation>
            <wsdl:input message="typens:portfolioProjectListRequest" />
            <wsdl:output message="typens:portfolioProjectListResponse" />
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectInfo">
            <wsdl:documentation>Retrieve project info</wsdl:documentation>
            <wsdl:input message="typens:portfolioProjectInfoRequest" />
            <wsdl:output message="typens:portfolioProjectInfoResponse" />
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectAdd">
            <wsdl:documentation>Add project</wsdl:documentation>
            <wsdl:input message="typens:portfolioProjectAddRequest" />
            <wsdl:output message="typens:portfolioProjectAddResponse" />
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectUpdate">
            <wsdl:documentation>Update project</wsdl:documentation>
            <wsdl:input message="typens:portfolioProjectUpdateRequest" />
            <wsdl:output message="typens:portfolioProjectUpdateResponse" />
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectRemove">
            <wsdl:documentation>Remove project</wsdl:documentation>
            <wsdl:input message="typens:portfolioProjectRemoveRequest" />
            <wsdl:output message="typens:portfolioProjectRemoveResponse" />
        </wsdl:operation>
        </wsdl:portType>
    <wsdl:binding name="{{var wsdl.handler}}Binding" type="typens:{{var wsdl.handler}}PortType">
        <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" />
        <wsdl:operation name="portfolioProjectList">
            <soap:operation soapAction="" />
            <wsdl:input>
                <soap:body use="literal" />
            </wsdl:input>
            <wsdl:output>
                <soap:body use="literal" />
            </wsdl:output>
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectInfo">
            <soap:operation soapAction="" />
            <wsdl:input>
                <soap:body use="literal" />
            </wsdl:input>
            <wsdl:output>
                <soap:body use="literal" />
            </wsdl:output>
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectAdd">
            <soap:operation soapAction="" />
            <wsdl:input>
                <soap:body use="literal" />
            </wsdl:input>
            <wsdl:output>
                <soap:body use="literal" />
            </wsdl:output>
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectUpdate">
            <soap:operation soapAction="" />
            <wsdl:input>
                <soap:body use="literal" />
            </wsdl:input>
            <wsdl:output>
                <soap:body use="literal" />
            </wsdl:output>
        </wsdl:operation>
        <wsdl:operation name="portfolioProjectRemove">
            <soap:operation soapAction="" />
            <wsdl:input>
                <soap:body use="literal" />
            </wsdl:input>
            <wsdl:output>
                <soap:body use="literal" />
            </wsdl:output>
        </wsdl:operation>
        </wsdl:binding>
    <wsdl:service name="{{var wsdl.name}}Service">
        <wsdl:port name="{{var wsdl.handler}}Port" binding="typens:{{var wsdl.handler}}Binding">
            <soap:address location="{{var wsdl.url}}" />
        </wsdl:port>
    </wsdl:service>
</wsdl:definitions>

O exemplo não se encaixou em uma resposta. Veja o restante dos arquivos aqui

_{Nota : Esses arquivos foram criados usando o Ultimate Module Creator . Acabei de adicionar alguns comentários nos arquivos xml.}

Infelizmente, o exemplo não se encaixou em uma resposta. Aqui estão os demais arquivos que você precisa:

Agora terminamos os XMLs. Vamos ao código:

app/code/local/Easylife/Portfolio/Model/Project/Api.php - modelo para lidar com os pedidos da API v1 (e alguns pedidos da V2)

<?php
class Easylife_Portfolio_Model_Project_Api extends Mage_Api_Model_Resource_Abstract{
    /**
     * init project
     * @access protected
     * @param $projectId
     * @return Easylife_Portfolio_Model_Project
     */
    protected function _initProject($projectId){
        $project = Mage::getModel('portfolio/project')->load($projectId);
        if (!$project->getId()) {
            $this->_fault('project_not_exists');
        }
        return $project;
    }
    /**
     * get projects
     * @access public
     * @param mixed $filters
     * @return array
     */
    public function items($filters = null){
        $collection = Mage::getModel('portfolio/project')->getCollection();
        $apiHelper = Mage::helper('api');
        $filters = $apiHelper->parseFilters($filters);
        try {
            foreach ($filters as $field => $value) {
                $collection->addFieldToFilter($field, $value);
            }
        } 
        catch (Mage_Core_Exception $e) {
            $this->_fault('filters_invalid', $e->getMessage());
        }
        $result = array();
        foreach ($collection as $project) {
            $result[] = $project->getData();
        }
        return $result;
    }
    /**
     * Add project
     * @access public
     * @param array $data
     * @return array
     */
    public function add($data){
        try {
            if (is_null($data)){
                throw new Exception(Mage::helper('portfolio')->__("Data cannot be null"));
            }
            $project = Mage::getModel('portfolio/project')
                ->setData((array)$data)
                ->save();
        } 
        catch (Mage_Core_Exception $e) {
            $this->_fault('data_invalid', $e->getMessage());
        } 
        catch (Exception $e) {
            $this->_fault('data_invalid', $e->getMessage());
        }
        return $project->getId();
    }

    /**
     * Change existing project information
     * @access public
     * @param int $projectId
     * @param array $data
     * @return bool
     */
    public function update($projectId, $data){
        $project = $this->_initProject($projectId);
        try {
            $project->addData((array)$data);
            $project->save();
        } 
        catch (Mage_Core_Exception $e) {
            $this->_fault('save_error', $e->getMessage());
        }

        return true;
    }
    /**
     * remove project
     * @access public
     * @param int $projectId
     * @return bool
     */
    public function remove($projectId){
        $project = $this->_initProject($projectId);
        try {
            $project->delete();
        } 
        catch (Mage_Core_Exception $e) {
            $this->_fault('remove_error', $e->getMessage());
        }
        return true;
    }
    /**
     * get info
     * @access public
     * @param int $projectId
     * @return array
     */
    public function info($projectId){
        $result = array();
        $project = $this->_initProject($projectId);
        $result = $project->getData();
        return $result;
    }
}

app/code/local/Easylife/Portfolio/Model/Project/Api/V2.php - modelo para lidar com as solicitações da API v2

<?php
class Easylife_Portfolio_Model_Project_Api_V2 extends Easylife_Portfolio_Model_Project_Api{
    /**
     * Project info
     * @access public
     * @param int $projectId
     * @return object
     */
    public function info($projectId){
        $result = parent::info($projectId);
        $result = Mage::helper('api')->wsiArrayPacker($result);
        return $result;
    }
}

É isso aí. Isso deve fornecer uma funcionalidade básica da API para sua entidade. Você pode adicionar seus métodos semelhantes aos já adicionados ou modificá-los para atender às suas necessidades.

_{Nota : Esses arquivos foram criados usando o Ultimate Module Creator . Acabei de adicionar alguns comentários nos arquivos xml.}