GitLab MCP Server

Instructions

Implementation Reference

• src/handlers/merge-requests.ts:164-194 (handler)

  Main handler function that executes the list_merge_request_diffs tool. Resolves merge request IID if source_branch provided, constructs GitLab API endpoint /merge_requests/{iid}/diffs with pagination and unidiff parameters, fetches data using GitLabClient, and returns JSON response.
  async listMergeRequestDiffs(args: ListMergeRequestDiffsParams) { const mergeRequestIid = await this.resolveMergeRequestIid( args.project_id, args.merge_request_iid, args.source_branch ); const params = new URLSearchParams(); if (args.page) params.append("page", String(args.page)); if (args.per_page) params.append("per_page", String(args.per_page)); if (args.unidiff !== undefined) params.append("unidiff", String(args.unidiff)); const queryString = params.toString(); const url = `/projects/${encodeURIComponent( args.project_id )}/merge_requests/${mergeRequestIid}/diffs${ queryString ? `?${queryString}` : "" }`; const data = await this.client.get(url); return { content: [ { type: "text", text: JSON.stringify(data, null, 2), }, ], }; }
• src/tools/merge-requests.ts:112-146 (schema)

  MCP tool schema definition for list_merge_request_diffs, including input schema with properties for project_id, merge_request_iid/source_branch, pagination, and unidiff.
  { name: 'list_merge_request_diffs', description: 'List merge request diffs with pagination support. Either merge_request_iid or source_branch must be provided.', inputSchema: { type: 'object', properties: { project_id: { type: 'string', description: 'Project ID or path', }, merge_request_iid: { type: 'number', description: 'Merge request internal ID', }, source_branch: { type: 'string', description: 'Source branch name (alternative to merge_request_iid)', }, page: { type: 'number', description: 'Page number for pagination (default: 1)', }, per_page: { type: 'number', description: 'Number of items per page (max: 100, default: 20)', maximum: 100, }, unidiff: { type: 'boolean', description: 'Present diffs in unified diff format (GitLab 16.5+)', }, }, required: ['project_id'], }, },
• src/server.ts:197-200 (registration)

  Tool dispatch registration in the MCP server request handler switch statement, calling the mergeRequestHandlers.listMergeRequestDiffs method.
  case "list_merge_request_diffs": return await this.mergeRequestHandlers.listMergeRequestDiffs( args as unknown as ListMergeRequestDiffsParams );
• src/types.ts:267-274 (schema)

  TypeScript interface defining the input parameters for the listMergeRequestDiffs handler.
  export interface ListMergeRequestDiffsParams { project_id: string; merge_request_iid?: number; source_branch?: string; page?: number; per_page?: number; unidiff?: boolean; }
• src/handlers/merge-requests.ts:32-76 (helper)

  Helper method to resolve merge request IID from project and source_branch if merge_request_iid not provided directly. Used by the handler.
  private async resolveMergeRequestIid( projectId: string, mergeRequestIid?: number, sourceBranch?: string ): Promise<number> { if (mergeRequestIid) { return mergeRequestIid; } if (!sourceBranch) { throw new Error( "Either merge_request_iid or source_branch must be provided" ); } // Find MR by source branch const mrs = (await this.client.get( `/projects/${encodeURIComponent( projectId )}/merge_requests?source_branch=${encodeURIComponent( sourceBranch )}&state=opened&per_page=1` )) as GitLabMergeRequest[]; if (!mrs || mrs.length === 0) { // Try all states if no open MR found const allMrs = (await this.client.get( `/projects/${encodeURIComponent( projectId )}/merge_requests?source_branch=${encodeURIComponent( sourceBranch )}&per_page=1` )) as GitLabMergeRequest[]; if (!allMrs || allMrs.length === 0) { throw new Error( `No merge request found for source branch: ${sourceBranch}` ); } return allMrs[0].iid; } return mrs[0].iid; }