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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely non-derivable behavior: the call is metered at $0.003 USDC via x402, which tells the agent this is a paid operation, and it lists the returned fields. It stops short of pagination/cost-cap or rate-limit detail, so not a 5.

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?

Purpose and filter capabilities are front-loaded in the first clause, with cost demoted to a short trailing sentence. It is a single dense sentence, but every element (filters, return fields, price) carries information rather than padding.

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 an 8-parameter, no-output-schema tool this covers what an agent needs: what it searches, how it can be narrowed, what comes back (stars, forks, license, topics, last push), and that the call costs money. The absent output schema is compensated by the inline return-field list, and the unmentioned 'limit' is the only minor gap.

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 only 50%, so the description has to compensate, and it largely does: it explains language, topic, minimum stars, created-or-pushed-after dates, and the stars/recent sort semantics for seven of the eight parameters. Only 'limit' is left unexplained and no extra syntax is added, keeping it below 5.

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 ('Find the best GitHub repositories') and enumerates the filter axes, so an agent knows this is a repository-discovery search rather than a code or issue search. It does not name the adjacent siblings (github_code, github_issues) to sharpen the boundary, so it lands at clear-but-undifferentiated rather than 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?

The phrase 'for anything' plus the filter list implies the usage context (broad repo discovery with language/topic/star/date narrowing), but there is no explicit when-to-use vs. when-not statement and no routing to github_code or github_issues for non-repository queries. Usage is inferable but not guided.

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