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

Annotations only declare readOnlyHint and openWorldHint; the description adds the real behavioral layer: omitted page/limit walks every page up to a 1,000-item cap with a truncated flag beyond it, while explicit page/limit returns a single page of at most 50. It also discloses the slimmed field set, so the caller knows what comes back.

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 tight sentences, front-loaded with scope and sorting, then pagination semantics, then return fields, then the sibling routing. No filler and no repetition of the title.

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?

No output schema exists, and the description compensates by enumerating the returned fields (full_name, description, private, fork, archived, language, counts, size, default_branch, URLs, dates). Combined with pagination and scope details, nothing an agent needs to call it correctly is missing.

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 coverage is 100%, but the schema only says '1-based page number' and 'results per page' with null defaults. The description resolves what is genuinely ambiguous: the default null behavior (walk all pages), the 50-per-page ceiling on limit, and the truncation outcome, which the schema alone cannot convey.

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 plus a precise scope: repos the account can work in, including own, org, and collaborator repos, with the sort order (case-insensitive by name). It draws a clear line against search_repos (instance-wide) and get_repo (single detail), so an agent can disambiguate 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?

Explicitly names both alternatives and the condition that selects them: search_repos for repos anywhere on the instance, get_repo for one repo's details. It also distinguishes the internal usage fork between streaming the whole set and paging, so the agent knows which call pattern to choose.

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