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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds value beyond that by disclosing the composition of the payload (PR description, commits, selected diff hunks), which matters because no output schema exists; it stops short of mentioning diff-size limits, truncation, or pagination.

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?

Two tight sentences, front-loaded with what the tool returns and followed by when to reach for it. No filler, no repetition of the tool name, and the most decision-relevant content (one PR, full picture) comes first.

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 and a read-only annotation set, the description responsibly sketches the return payload and the intended downstream use. What is missing is edge behavior an agent would want — behavior for invalid/nonexistent PR numbers and how much diff is returned — but for a simple two-parameter read tool this is close to complete.

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 50%: 'repo' is documented in the schema while 'prNumber' is bare. The description mentions no parameters at all, so it neither clarifies repo format (owner/name) nor adds anything to the self-evident prNumber. Baseline 3 applies given partial schema coverage.

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 gives a specific resource ('one pull request') and enumerates what the response contains: description, commits, and the tellings parts of the diff. The singular framing clearly separates it from the plural sibling list_github_changes and from get_github_file, so an agent can route correctly without opening a schema.

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 states two concrete usage contexts: explaining changes in plain language for a user, and preparing to write a post about them. That is clear when-to-use guidance, but it never names an alternative tool or a when-not-to-use condition (e.g., use list_github_changes to browse many PRs).

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