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

The annotations already cover safety (readOnlyHint, openWorldHint), but the description adds critical context: data limitations ('videos are not included'), error behavior (404 for unknown usernames), and a detailed pricing model ($0.002 USDC per successful call, x402 payment, no charge on failure). This extra behavioral detail is exactly what an agent needs before invoking a paid data-fetching tool.

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?

The description is front-loaded with the tool's core purpose, followed by essential limitations, error behavior, and pricing. Every sentence earns its place, and the information is organized logically for quick scanning.

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?

Given the tool's simplicity (one parameter, output schema present, annotations providing safety hints), the description covers everything an agent needs: what data is returned, what is missing, how errors manifest, and the cost model. Nothing critical is omitted.

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 username parameter's accepted formats are fully documented. The description adds no further meaning about the parameter beyond reiterating that unknown usernames produce a 404, so the baseline 3 is appropriate.

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 resource ('Public TikTok profile') and enumerates the exact fields returned, making the tool's output unmistakable. It implicitly distinguishes from sibling tools by noting that videos are not included, but it does not explicitly name a sibling or a verb like 'get', so it falls just short of 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?

The description implies usage by stating the tool fetches a public profile and noting that unknown usernames return 404, but it offers no explicit 'use this when...' guidance or named alternatives. An agent can infer the purpose, but routing decisions are left to the sibling names.

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