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

The description adds the auth requirement and return value ({state}) beyond what annotations provide. It also states 'without merging,' which clarifies behavior. The idempotent claim is redundant with annotations, but the extra context about auth and return is valuable. 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?

The description is a single sentence that front-loads the primary action, then provides necessary context (auth, idempotency, return). It is concise, with no filler words, and every clause adds value.

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 3-parameter tool with no output schema, the description covers the essential aspects: purpose, auth, idempotency, and return value. It doesn't discuss error handling (e.g., if PR is already closed), but that is not critical for a basic tool. The information is sufficient for an agent to call it correctly.

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%, so the schema already documents all three parameters (owner, repo, number). The description does not add any additional parameter-specific meaning, so it meets the baseline for high coverage without further elaboration.

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 clearly states the action: 'Close an open pull request without merging.' It specifies the resource (pull request) and the distinguishing condition (without merging), which differentiates it from merge_pr and close_issue. The verb 'close' is specific and unambiguous.

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 description implies the use case by saying 'without merging,' which contrasts with merge_pr, but it doesn't explicitly name alternatives or state when not to use it. It does provide a prerequisite ('Requires authenticated caller with write access'), which gives context but not explicit exclusions.

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