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

Beyond the annotations (destructiveHint=true, idempotentHint=true, openWorldHint=true), the description adds the irreversible nature of the merge, the missions:write scope requirement, the auto-branch-update and auto-conflict-fix behavior, and the meaning of the 202/409 responses. That is rich behavioral context an agent cannot get from structured fields.

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?

The core action and its irreversibility lead, followed by outcome handling; every sentence carries operational information. It is dense but slightly long, and the response-handling clauses could be tightened without losing meaning.

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?

With no output schema, the description covers the failure/async paths (202, 409, conflict auto-fix), permissions, and irreversibility, which is most of what an agent needs. It does not describe the shape of a successful merge response, which is a minor remaining gap.

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?

There is a single required parameter with 100% schema coverage, so the schema already documents issueId fully (Linear key or GitHub Issues id). The description adds no parameter-level detail beyond the schema, which is the expected baseline of 3.

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 description names a specific verb and resource ('Merge the mission's open pull request on GitHub') and states the repository's own merge method is used, so the action is unmistakable. It does not differentiate itself from adjacent siblings such as set_mission_auto_merge or set_mission_disposition, which is the one gap preventing a 5.

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?

It gives clear conditional guidance on how to proceed in each outcome: 202 updating_branch means stop calling, 409 means a blocker exists and the reason is returned, and a merge conflict is handled automatically with no further call. What is missing is an explicit when-not-to-use or a named alternative to choose instead.

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