GitLab MCP Server

get_merge_request_diffs

Retrieve code changes and differences for GitLab merge requests to review modifications between branches or versions.

Instructions

Get the changes/diffs of a merge request (Either mergeRequestIid or branchName must be provided)

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "project_id": "<project_id>"
    },
    "name": "get_merge_request_diffs"
  }
}

Input Schema

Name	Required	Description
`project_id`	Yes	Project ID or complete URL-encoded path to project
`merge_request_iid`	No	The IID of a merge request
`source_branch`	No	Source branch name
`view`	No	Diff view type

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv1.0.0Jan 3, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
First observedNov 16, 2025

TDQS

B3.2/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions the need for 'mergeRequestIid or branchName' but doesn't describe what the tool returns (e.g., diff format, pagination, error handling), whether it requires authentication, or any rate limits. This leaves significant gaps for a tool that likely fetches detailed data.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that front-loads the core purpose and includes essential parameter guidance. There is no wasted text, and it's structured to convey key information immediately.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of fetching merge request diffs (which could involve large data sets or specific formats), no annotations, and no output schema, the description is incomplete. It lacks details on return values, error conditions, or behavioral traits, making it inadequate for full agent understanding without additional context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents all parameters thoroughly. The description adds minimal value by implying that 'mergeRequestIid or branchName' (likely referring to 'source_branch' in the schema) is required, but this is partially redundant with schema details. Baseline 3 is appropriate as the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Get the changes/diffs') and resource ('of a merge request'), which is specific and unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'get_branch_diffs' or 'get_merge_request', which might have overlapping functionality.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides implied usage guidance by stating 'Either mergeRequestIid or branchName must be provided', which helps understand parameter requirements. However, it doesn't explicitly say when to use this tool versus alternatives like 'get_branch_diffs' or 'get_merge_request', nor does it mention any prerequisites or exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.