get_case_citator

Instructions

Implementation Reference

• src/index.ts:297-347 (handler)

  The main handler for the get_case_citator tool. It registers an MCP tool that accepts language, databaseId, caseId, metadataType, and optional date parameters, then fetches citation data from the CanLII API at /v1/caseCitator/{language}/{databaseId}/{caseId}/{metadataType}. It parses the response using the appropriate schema (CitedCasesResponseSchema, CitingCasesResponseSchema, or CitedLegislationsResponseSchema) based on the metadataType and returns the result.

  // TOOL: get_case_citator
  // ============================================================
  server.tool(
  	"get_case_citator",
  	"Look up citation relationships for a case. Critical for verifying if a case is still good law. " +
  	"Use 'citingCases' to see what later cases cite this decision — if many recent cases cite it approvingly, it is strong authority. " +
  	"Use 'citedCases' to see what authorities this case relied on. " +
  	"Use 'citedLegislations' to see what statutes the case references. " +
  	"Returns the full list of citing/cited items.",
  	{
  		language: z.enum(["en", "fr"]).default("en")
  			.describe("Language: 'en' for English (default), 'fr' for French"),
  		databaseId: pathSegmentSchema
  			.describe("Court database ID (e.g., 'onsc', 'onca', 'csc-scc')"),
  		caseId: pathSegmentSchema
  			.describe("Case unique identifier (e.g., '2021onsc8582')"),
  		metadataType: z.enum(["citedCases", "citingCases", "citedLegislations"])
  			.describe("'citingCases' = what later cases cite this one (check if still good law); 'citedCases' = what this case relies on; 'citedLegislations' = statutes referenced"),
  		...dateParametersSchema,
  	},
  	async (params) => {
  		try {
  			const { language, databaseId, caseId, metadataType, ...dateParams } = params;
  			const urlParams = new URLSearchParams({ api_key: apiKey });
  			buildDateParams(urlParams, dateParams);
  
  			const response = await apiFetch(
  				`https://api.canlii.org/v1/caseCitator/${language}/${encodeURIComponent(databaseId)}/${encodeURIComponent(caseId)}/${metadataType}?${urlParams.toString()}`
  			);
  
  			if (!response.ok) {
  				return errorResponse(`Error: Failed to fetch case citator data (${response.status})`);
  			}
  
  			const data = await response.json();
  
  			const schemaMap = {
  				citedCases: CitedCasesResponseSchema,
  				citingCases: CitingCasesResponseSchema,
  				citedLegislations: CitedLegislationsResponseSchema,
  			} as const;
  
  			const parsed = schemaMap[metadataType].parse(data);
  			return jsonResponse(parsed);
  		} catch (error) {
  			return errorResponse(
  				`Error: ${error instanceof Error ? error.message : "Unknown error"}`
  			);
  		}
  	}
  );

• src/schema.ts:28-30 (schema)

  Zod schema for CitedCasesResponse — validates the response when metadataType is 'citedCases', expects an object with an array of CaseSchema under the 'citedCases' key.

  export const CitedCasesResponseSchema = z.object({
      citedCases: z.array(CaseSchema),
  }).passthrough();

• src/schema.ts:32-34 (schema)

  Zod schema for CitingCasesResponse — validates the response when metadataType is 'citingCases', expects an object with an array of CaseSchema under the 'citingCases' key.

  export const CitingCasesResponseSchema = z.object({
      citingCases: z.array(CaseSchema),
  }).passthrough();

• src/schema.ts:92-94 (schema)

  Zod schema for CitedLegislationsResponse — validates the response when metadataType is 'citedLegislations', expects an object with an array of LegislationItemSchema under the 'citedLegislations' key.

  export const CitedLegislationsResponseSchema = z.object({
      citedLegislations: z.array(LegislationItemSchema),
  }).passthrough();

• src/index.ts:299-316 (registration)

  Tool registration for get_case_citator via server.tool(), defining the tool name, description, and input schema including language, databaseId, caseId, metadataType, and date parameters.

  server.tool(
  	"get_case_citator",
  	"Look up citation relationships for a case. Critical for verifying if a case is still good law. " +
  	"Use 'citingCases' to see what later cases cite this decision — if many recent cases cite it approvingly, it is strong authority. " +
  	"Use 'citedCases' to see what authorities this case relied on. " +
  	"Use 'citedLegislations' to see what statutes the case references. " +
  	"Returns the full list of citing/cited items.",
  	{
  		language: z.enum(["en", "fr"]).default("en")
  			.describe("Language: 'en' for English (default), 'fr' for French"),
  		databaseId: pathSegmentSchema
  			.describe("Court database ID (e.g., 'onsc', 'onca', 'csc-scc')"),
  		caseId: pathSegmentSchema
  			.describe("Case unique identifier (e.g., '2021onsc8582')"),
  		metadataType: z.enum(["citedCases", "citingCases", "citedLegislations"])
  			.describe("'citingCases' = what later cases cite this one (check if still good law); 'citedCases' = what this case relies on; 'citedLegislations' = statutes referenced"),
  		...dateParametersSchema,
  	},