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 genuinely useful behavior beyond that: what happens on a miss (it says so) and why a repo may be absent (unknown or excluded for fake stars). Auth, rate limits, and freshness/caching are unaddressed, keeping it out of the top band.

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 sentences, each doing distinct work: payload contents, usage context, and miss behavior. The field enumeration is long but front-loads the value; nothing is padded, though the list could be tightened.

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?

A single-repo lookup with an output schema, full param coverage, and clear annotations is well covered; the description sensibly adds the negative-case behavior the schema cannot express. Enumerating return fields is mildly redundant given the output schema, but 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 description coverage is 100%, so the schema already documents 'owner/name' or URL and the locale enum with its Spanish-use guidance. The description's '(owner/name or URL)' and return-field list add no parameter semantics beyond the schema, making the baseline 3 correct.

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 — retrieve everything RepoAlerts knows about a single GitHub repository — and enumerates the data returned (stars, star curve, licence, last push, replacements, HN stories, similar repos). The single-repo scope implicitly separates it from the search/discovery siblings, but no sibling is named explicitly, so it falls short of full sibling differentiation.

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?

'Use it to check a repo before recommending or installing it' gives a clear use context. However, it offers no when-not guidance and never points at find_alternatives, search_repos, or trending_repos as the alternative for discovery-style queries.

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