Create GitLab merge request

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

Annotations already establish mutation (readOnlyHint=false) and non-idempotency (idempotentHint=false), so the description has a lower bar. It adds minor context (source branch must exist; draft mode is available) but does not disclose side effects like pipeline triggers, duplicate MRs on re-invocation, or permission requirements. No contradiction with annotations.

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

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

Two sentences with zero waste: the first states the core action and input constraint, the second highlights the draft capability. It is front-loaded and appropriately sized for a purpose statement.

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

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

For a 14-parameter creation tool with 4 required fields, a two-sentence description is thin. It does not explain preconditions beyond branch existence, key default behaviors (squash, collaboration, branch removal), or cross-project creation via target_project_id. The output schema covers return values, but operational context for correct invocation is largely missing.

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

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

Schema description coverage is only 7% (just 'project' is documented), leaving 13 parameters unexplained. The description names only source_branch and draft, and does not compensate for the large gap—target_branch, squash, labels, assignee_ids, reviewer_ids, remove_source_branch, target_project_id (cross-project MRs), and milestone_id all lack meaning.

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

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

The title and description together clearly identify the action (create) and resource (a GitLab merge request), with 'from an existing source branch' framing the input. It distinguishes from sibling tools like list/get/update/merge/rebase_merge_request, though the verb 'open' is slightly ambiguous on its own (resolved by the title 'Create').

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

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

'From an existing source branch' implies a precondition, and 'Draft merge requests are supported' hints at a capability, but there is no explicit when-to-use vs. alternative guidance. No mention of when to prefer update_merge_request, merge_merge_request, or list_merge_requests, and no exclusions are stated.

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