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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description still adds a genuinely new trait not present in structured fields: a concrete cost of 1 credit per request, which matters for agent budgeting. It does not discuss pagination limits or result-size behaviour, but the cursor parameter covers paging in the schema.

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 short clauses, front-loaded with the core action, followed by the safety statement and the cost. No filler and nothing redundant beyond a brief restatement of read-only for emphasis.

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 a four-parameter read-only list tool with full schema coverage and no output schema, the description plus schema is sufficient to call it correctly. The remaining gap is routing context against similarly named GitHub listing and search siblings, which the description never addresses.

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 count bounds, the order enum, cursor semantics and the username format all documented inline. The description adds no additional meaning about these parameters, so the baseline 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 description states a specific verb and resource ("List a GitHub user's public repositories") and makes the public-only scope explicit, so the agent knows exactly what is fetched. It does not differentiate from close siblings like github_search_repositories or github_list_starred, which is the only thing keeping it from a 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 guidance on when to choose this over github_search_repositories, github_list_starred, or github_list_projects. The only implied condition is that you need a named user's repos, which the agent must infer from the title alone.

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