GitLab MCP Server

Instructions

Implementation Reference

• src/handlers/merge-requests.ts:196-217 (handler)

  The core handler function that implements the get_branch_diffs tool logic: constructs the GitLab repository/compare API URL and fetches/returns the diffs as JSON.

  async getBranchDiffs(args: GetBranchDiffsParams) {
    const params = new URLSearchParams();
    params.append("from", args.from);
    params.append("to", args.to);
    if (args.straight !== undefined)
      params.append("straight", String(args.straight));
  
    const url = `/projects/${encodeURIComponent(
      args.project_id
    )}/repository/compare?${params.toString()}`;
  
    const data = await this.client.get(url);
  
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(data, null, 2),
        },
      ],
    };
  }

• src/tools/merge-requests.ts:147-172 (schema)

  Tool definition including the input schema (JSON Schema) for validating parameters: project_id, from, to, straight.

  {
    name: 'get_branch_diffs',
    description: 'Get the changes/diffs between two branches or commits in a GitLab project',
    inputSchema: {
      type: 'object',
      properties: {
        project_id: {
          type: 'string',
          description: 'Project ID or path',
        },
        from: {
          type: 'string',
          description: 'The base branch or commit SHA to compare from',
        },
        to: {
          type: 'string',
          description: 'The target branch or commit SHA to compare to',
        },
        straight: {
          type: 'boolean',
          description: 'Comparison method: false for "..." (default), true for "--"',
        },
      },
      required: ['project_id', 'from', 'to'],
    },
  },

• src/server.ts:201-204 (registration)

  Server-side dispatch/registration in the CallToolRequestSchema handler switch statement that routes calls to the mergeRequestHandlers.getBranchDiffs method.

  case "get_branch_diffs":
    return await this.mergeRequestHandlers.getBranchDiffs(
      args as unknown as GetBranchDiffsParams
    );

• src/types.ts:276-281 (schema)

  TypeScript type definition/interface for the GetBranchDiffsParams used in handler signature and server dispatch.

  export interface GetBranchDiffsParams {
    project_id: string;
    from: string;
    to: string;
    straight?: boolean;
  }