gitlab-ci-mcp

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gitlab_compare_branches

Read-onlyIdempotent

Compare two GitLab branches to list up to 30 commits and changed files, supporting release-note drafting and branch difference checks.

Instructions

Compare two branches — returns up to 30 commits and the list of changed files.

Use for "what's in release/x.y vs master?" or for release-note drafting.

Examples: - "What's new in release/1.5 vs master" → source='release/1.5', target='master' - Don't use to fetch full diffs of an MR — use gitlab_get_merge_request_changes.

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": {
      "source": "<source>",
      "project_path": "<project_path>"
    },
    "name": "gitlab_compare_branches"
  }
}

Input Schema

Name	Required	Description	Default
`source`	Yes	Source branch/tag/SHA.
`target`	No	Target branch (default 'master').	master
`project_path`	Yes	GitLab project path (e.g. 'my-org/my-repo'). Required by default. For legacy deployments only, set GITLAB_ALLOW_DEFAULT_PROJECT=true to use GITLAB_PROJECT_PATH when omitted.

Output Schema

Name	Required	Description	Default
`source`	Yes
`target`	Yes
`commits`	Yes
`diffs_count`	Yes
`changed_files`	Yes
`commits_count`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedv0.5.5Nov 5, 2026

removedInput schema / properties / project_path / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

removedInput schema / properties / project_path / default
```
Removed value: -null
```

changedInput schema / properties / project_path / description

Previous value: -"GitLab project path (e.g. 'my-org/my-repo'). When omitted, the default from GITLAB_PROJECT_PATH env var is used."New value: +"GitLab project path (e.g. 'my-org/my-repo'). Required by default. For legacy deployments only, set GITLAB_ALLOW_DEFAULT_PROJECT=true to use GITLAB_PROJECT_PATH when omitted."

addedInput schema / properties / project_path / minLength
```
Added value: +1
```
addedInput schema / properties / project_path / type
```
Added value: +"string"
```

changedInput schema / required

Previous value: -[
-  "source"
-]New value: +[
+  "source",
+  "project_path"
+]

First observedv0.5.1Apr 17, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered; the description adds genuine behavioral context by disclosing the 30-commit cap and that changed files are included. It stops short of explaining ordering or what happens when the cap is hit.

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?

Front-loads the action and return shape in one sentence, then a usage sentence, then two compact examples with the exclusion last. No filler; every line earns its place.

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

Completeness5/5

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

For a three-parameter read-only comparison tool with a 100%-covered schema and an output schema, this is complete: purpose, call shape, direction of comparison, result cap, and sibling routing are all present.

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 coverage is 100%, so the schema already documents all three parameters and the baseline of 3 applies. The worked example does clarify comparison direction (source='release/1.5', target='master'), which the schema's terse "Source branch/tag/SHA" does not spell out, but this is a modest addition.

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

Purpose5/5

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

States a specific verb and resource ("Compare two branches") plus the return payload (up to 30 commits and changed files), which lets an agent recognize it instantly against siblings like gitlab_list_branches or gitlab_get_merge_request_changes.

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

Usage Guidelines5/5

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

Gives explicit when-to-use framing ("what's in release/x.y vs master?" and release-note drafting) and an explicit when-not-to-use rule that names the correct alternative, gitlab_get_merge_request_changes, for full MR diffs.

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