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

Annotations already declare destructiveHint=true and idempotentHint=true, so the repeated 'Idempotent' earns no credit, but the description does add value beyond annotations by naming the write-access/auth requirement and the return payload shape ({state}). It stops short of saying what the close does to the branch or whether it is reversible.

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?

Four terse sentences, front-loaded with the action and its scope, followed by permission, idempotency, and return value. Only 'Idempotent.' is redundant with the annotations, and it costs almost nothing.

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 full annotation coverage of the safety profile and no output schema, the description covers action, auth requirement, idempotency, and return shape. The only remaining gap is downstream effect (does closing delete the branch or leave commit history intact), which is a minor omission here.

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% — owner, repo, and number are all documented in the schema — and the description adds nothing about their meaning or format. Baseline 3 applies since the schema carries the parameter burden entirely.

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 pull request') and immediately narrows scope with 'without merging', which is exactly the distinction an agent needs against siblings like merjax_merge_pr, merjax_approve_pr, and merjax_update_pr.

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?

'Without merging' implicitly routes the agent away from merge_pr and gives a clear precondition (an open PR, authenticated caller with write access), but it never explicitly names an alternative or states a when-not condition beyond the merge exclusion.

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