General example

{
  "resourceType" : "SearchParameter",
  "id" : "example",
  "extension" : [{
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode" : "fhir"
  }],
  "url" : "http://hl7.org/fhir/SearchParameter/example",
  "version" : "1",
  "name" : "IDSEARCHPARAMETER",
  "title" : "I D- S E A R C H- P A R A M E T E R",
  "derivedFrom" : "http://hl7.org/fhir/SearchParameter/Resource-id",
  "status" : "draft",
  "experimental" : true,
  "date" : "2013-10-23",
  "publisher" : "HL7 International / FHIR Infrastructure",
  "contact" : [{
    "telecom" : [{
      "system" : "url",
      "value" : "http://www.hl7.org/Special/committees/fiwg"
    }]
  }],
  "description" : "Search by resource identifier - e.g. same as the read interaction, but can return included resources",
  "useContext" : [{
    "code" : {
      "system" : "http://terminology.hl7.org/CodeSystem/usage-context-type",
      "code" : "focus"
    },
    "valueCodeableConcept" : {
      "coding" : [{
        "system" : "http://terminology.hl7.org/CodeSystem/variant-state",
        "code" : "positive"
      }]
    }
  }],
  "jurisdiction" : [{
    "coding" : [{
      "system" : "urn:iso:std:iso:3166",
      "code" : "US",
      "display" : "United States of America"
    }]
  }],
  "purpose" : "Need to search by identifier for various infrastructural cases - mainly retrieving packages, and matching as part of a chain",
  "code" : "_id",
  "base" : ["Resource"],
  "type" : "token",
  "expression" : "id",
  "processingMode" : "normal"
}