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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is fully covered. The description adds one genuinely useful behavioral note not in the annotations: the PR description is truncated to the first 4,000 characters. It says nothing about behavior for a missing/inaccessible PR or permission requirements, so this is additive but thin.

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?

A single front-loaded sentence that opens with the action and then lists returned fields in a scannable way; no filler and no repetition of the title. The comma-enumerated field list is long but every item carries information.

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 an output schema present, return values need not be re-explained, and the annotations cover the read-only safety profile, so the remaining load is light. The one meaningful omission is sibling routing guidance for an agent choosing among several pull-request readers.

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 both 'repo' (owner/name format) and 'number' documented in the schema itself. The description adds no additional parameter meaning, so the baseline of 3 applies.

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 verb 'Returns' plus the resource 'a pull request's summary' is specific, and the enumerated fields (title, author, branches, size, mergeability, reviewers, description) clearly scope what 'summary' means. It does not explicitly contrast itself with sibling readers like get_pull_request_checks or list_pull_request_files, so it stays just short of 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?

There is no statement of when to use this tool versus the siblings that also read pull-request data (checks, files, review requests). The agent must infer routing from names alone, which is exactly the gap usage guidance is supposed to close.

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