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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotentHint=true, so the idempotency sentence repeats structured data rather than adding to it. The description does add value beyond annotations by stating the auth/write-access requirement and the return shape {state}, but it says nothing about what side effects closing produces or how it relates to the existing reopen tool.

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?

Three short sentences, with the action front-loaded and each sentence carrying distinct information: what it does, what it requires, and what it returns. There is no filler.

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 simple three-parameter mutation with no output schema, the description covers the action, the auth prerequisite, idempotency, and the return value, which is close to what an agent needs to call it correctly. The only notable gap is that it does not point to merjax_reopen_issue as the inverse operation.

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 100%, with owner, repo, and number each documented in the schema, so the baseline of 3 applies. The description adds no additional meaning about parameter formats or constraints beyond what the schema already provides.

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?

States a specific verb and resource ("Close an open issue"), which is enough to separate it from merjax_close_pr, merjax_reopen_issue, and merjax_comment_issue. It does not explicitly name a sibling, so it stops short of the top score.

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?

The prerequisite "Requires authenticated caller with write access" gives a real usage condition, and "closing an already-closed issue is a no-op" tells the agent it can call it without pre-checking state. There is no explicit guidance on when to prefer this over siblings such as merjax_reopen_issue or merjax_label_issue.

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