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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds genuinely new behavior by disclosing the paid path ($0.05 USDC per successful call via x402 on Base or Solana when no API key is supplied) and that only public data is collected. It stops short of describing failure/rate-limit behavior.

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 sentences: the capability list is front-loaded and the pricing caveat follows as a second, clearly separable clause. The data enumeration is long but each item conveys distinct output content rather than filler.

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 read-only single-parameter lookup with no output schema, the description usefully enumerates what is returned, which is exactly the missing structured information. Remaining gaps (response shape, error/payment-failure handling) are modest at this complexity level.

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?

With a single parameter and 100% schema description coverage (including the 'leading @ is stripped' normalization rule), the schema carries the semantics. The description says nothing additional about the username argument beyond implying it identifies a GitHub profile, 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 enumerates the concrete resource surfaced (repositories, languages, organisations, SSH/GPG keys, commit author emails, activity by hour/weekday), which is far more specific than the name 'github_user' alone. It is implicitly differentiated from generic siblings like osint-username or username_scanner by being GitHub-specific, but it never explicitly contrasts with them, keeping it below 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 when-to-use or when-not-to-use statement, no prerequisites, and no mention of the near neighbours (osint-username, username_scanner) that an agent must choose between. Usage is only inferable from the tool name and the data list.

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