GitLab MCP Server

Instructions

Implementation Reference

• src/handlers/merge-requests.ts:250-300 (handler)

  The main handler function that executes the update_merge_request tool logic. Resolves the merge request IID using helper if not provided, conditionally builds the update payload from input parameters, performs a PUT request to the GitLab API to update the merge request, and returns the response.
  async updateMergeRequest(args: UpdateMergeRequestParams) { const mergeRequestIid = await this.resolveMergeRequestIid( args.project_id, args.merge_request_iid, args.source_branch ); const requestData: any = {}; // Only include provided parameters if (args.title !== undefined) requestData.title = args.title; if (args.description !== undefined) requestData.description = args.description; if (args.state_event !== undefined) requestData.state_event = args.state_event; if (args.target_branch !== undefined) requestData.target_branch = args.target_branch; if (args.assignee_id !== undefined) requestData.assignee_id = args.assignee_id; if (args.assignee_ids !== undefined) requestData.assignee_ids = args.assignee_ids; if (args.reviewer_ids !== undefined) requestData.reviewer_ids = args.reviewer_ids; if (args.milestone_id !== undefined) requestData.milestone_id = args.milestone_id; if (args.labels !== undefined) requestData.labels = args.labels; if (args.remove_source_branch !== undefined) requestData.remove_source_branch = args.remove_source_branch; if (args.squash !== undefined) requestData.squash = args.squash; if (args.allow_collaboration !== undefined) requestData.allow_collaboration = args.allow_collaboration; if (args.merge_when_pipeline_succeeds !== undefined) requestData.merge_when_pipeline_succeeds = args.merge_when_pipeline_succeeds; const data = await this.client.put( `/projects/${encodeURIComponent( args.project_id )}/merge_requests/${mergeRequestIid}`, requestData ); return { content: [ { type: "text", text: JSON.stringify(data, null, 2), }, ], }; }
• src/tools/merge-requests.ts:221-297 (schema)

  MCP tool definition object including the name 'update_merge_request', description, and detailed inputSchema (JSON Schema) defining parameters, types, descriptions, enums, and requirements.
  { name: 'update_merge_request', description: 'Update an existing merge request. 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)', }, title: { type: 'string', description: 'Update merge request title', }, description: { type: 'string', description: 'Update merge request description (max 1,048,576 characters)', }, state_event: { type: 'string', enum: ['close', 'reopen'], description: 'Change the state (close or reopen the MR)', }, target_branch: { type: 'string', description: 'Change the target branch', }, assignee_id: { type: 'number', description: 'Assign a user to the merge request (use 0 to unassign)', }, assignee_ids: { type: 'array', items: { type: 'number' }, description: 'Assign multiple users to the merge request', }, reviewer_ids: { type: 'array', items: { type: 'number' }, description: 'Set reviewers for the merge request', }, milestone_id: { type: 'number', description: 'Assign a milestone (use 0 to remove)', }, labels: { type: 'string', description: 'Update labels (comma-separated)', }, remove_source_branch: { type: 'boolean', description: 'Flag to remove source branch after merging', }, squash: { type: 'boolean', description: 'Toggle squash commits on merge', }, allow_collaboration: { type: 'boolean', description: 'Allow commits from members who can merge', }, merge_when_pipeline_succeeds: { type: 'boolean', description: 'Set MR to merge when pipeline succeeds', }, }, required: ['project_id'], }, },
• src/server.ts:189-192 (registration)

  Dispatch/registration case in the main tool call handler switch statement that routes 'update_merge_request' calls to the mergeRequestHandlers.updateMergeRequest method.
  case "update_merge_request": return await this.mergeRequestHandlers.updateMergeRequest( args as unknown as UpdateMergeRequestParams );
• src/types.ts:295-312 (schema)

  TypeScript interface defining the input parameters for the updateMergeRequest handler, used for type safety across the codebase.
  export interface UpdateMergeRequestParams { project_id: string; merge_request_iid?: number; source_branch?: string; title?: string; description?: string; state_event?: 'close' | 'reopen'; target_branch?: string; assignee_id?: number; assignee_ids?: number[]; reviewer_ids?: number[]; milestone_id?: number; labels?: string; remove_source_branch?: boolean; squash?: boolean; allow_collaboration?: boolean; merge_when_pipeline_succeeds?: boolean; }
• src/handlers/merge-requests.ts:32-76 (helper)

  Helper method used by updateMergeRequest (and others) to resolve merge request IID from source branch name if not directly provided.
  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; }