create_mr_discussion

Add comments to GitLab merge requests for general feedback or specific code line discussions to facilitate code review and collaboration.

Instructions

Create a new discussion on a merge request. Can be a general discussion or an inline comment on the diff

Input Schema

TableJSON Schema

Name	Required	Description
`project_id`	Yes	Project ID or path
`merge_request_iid`	Yes	Merge request internal ID
`body`	Yes	The content of the discussion (supports Markdown)
`position`	No	Position for inline/diff comments. Required fields: base_sha, start_sha, head_sha, old_path, new_path. Use new_line for additions, old_line for deletions, both for context lines.

Implementation Reference

src/handlers/merge-requests.ts:425-463 (handler)

The handler function that executes the tool: creates a new discussion thread on a GitLab merge request, supporting inline diff positions, by calling the GitLab Discussions API endpoint.

async createMRDiscussion(args: CreateMRDiscussionParams) {
  const requestData: Record<string, unknown> = {
    body: args.body,
  };

  // Add position for inline/diff comments
  if (args.position) {
    requestData.position = {
      base_sha: args.position.base_sha,
      start_sha: args.position.start_sha,
      head_sha: args.position.head_sha,
      old_path: args.position.old_path,
      new_path: args.position.new_path,
      position_type: args.position.position_type || "text",
      ...(args.position.old_line !== undefined && {
        old_line: args.position.old_line,
      }),
      ...(args.position.new_line !== undefined && {
        new_line: args.position.new_line,
      }),
    };
  }

  const data = await this.client.post(
    `/projects/${encodeURIComponent(args.project_id)}/merge_requests/${
      args.merge_request_iid
    }/discussions`,
    requestData
  );

  return {
    content: [
      {
        type: "text",
        text: JSON.stringify(data, null, 2),
      },
    ],
  };
}

src/tools/merge-requests.ts:400-468 (schema)

MCP tool definition including name, description, and inputSchema for validating parameters like project_id, merge_request_iid, body, and optional position for inline comments.

{
  name: 'create_mr_discussion',
  description:
    'Create a new discussion on a merge request. Can be a general discussion or an inline comment on the diff',
  inputSchema: {
    type: 'object',
    properties: {
      project_id: {
        type: 'string',
        description: 'Project ID or path',
      },
      merge_request_iid: {
        type: 'number',
        description: 'Merge request internal ID',
      },
      body: {
        type: 'string',
        description: 'The content of the discussion (supports Markdown)',
      },
      position: {
        type: 'object',
        description:
          'Position for inline/diff comments. Required fields: base_sha, start_sha, head_sha, old_path, new_path. Use new_line for additions, old_line for deletions, both for context lines.',
        properties: {
          base_sha: {
            type: 'string',
            description: 'Base commit SHA (merge request target branch HEAD)',
          },
          start_sha: {
            type: 'string',
            description:
              'SHA of the commit when the MR was created (typically same as base_sha)',
          },
          head_sha: {
            type: 'string',
            description: 'HEAD commit SHA of the merge request source branch',
          },
          old_path: {
            type: 'string',
            description:
              'File path before the change (use same as new_path for new files)',
          },
          new_path: {
            type: 'string',
            description: 'File path after the change',
          },
          position_type: {
            type: 'string',
            enum: ['text'],
            description: 'Type of position (text for code comments)',
            default: 'text',
          },
          old_line: {
            type: 'number',
            description:
              'Line number in old version (for deleted lines or context)',
          },
          new_line: {
            type: 'number',
            description:
              'Line number in new version (for added lines or context)',
          },
        },
        required: ['base_sha', 'start_sha', 'head_sha', 'old_path', 'new_path'],
      },
    },
    required: ['project_id', 'merge_request_iid', 'body'],
  },
},

src/server.ts:219-222 (registration)
Server-side registration: switch case that dispatches tool calls to the mergeRequestHandlers.createMRDiscussion method.
```
case "create_mr_discussion":
  return await this.mergeRequestHandlers.createMRDiscussion(
    args as unknown as CreateMRDiscussionParams
  );
```

src/types.ts:491-505 (schema)

TypeScript interface defining the input parameters for the createMRDiscussion handler, matching the tool schema.

export interface CreateMRDiscussionParams {
  project_id: string;
  merge_request_iid: number;
  body: string;
  position?: {
    base_sha: string;
    start_sha: string;
    head_sha: string;
    old_path: string;
    new_path: string;
    position_type?: 'text';
    old_line?: number;
    new_line?: number;
  };
}

GitLab MCP Server