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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds value by specifying the exact return fields (bio, counts, verification, etc.), which is not in the annotations. It does not mention rate limits or authentication, but for a public read-only fetch, the added field list justifies a 4.

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 a single, efficient sentence that front-loads the action and resource, then lists the returned fields. Every clause earns its place; there is no redundancy or 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 simple one-parameter, read-only tool with complete schema documentation and no output schema, the description is sufficiently complete. It states exactly what data will be returned, and the annotations cover the operational safety. No critical information an agent needs to invoke 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%, and the single parameter 'username' is fully documented in the schema with format ('with or without @') and requiredness. The description does not add any additional parameter semantics beyond what the schema already provides, so the baseline of 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 clearly states the action ('Fetch') and the resource ('public profile information from TikTok'), and enumerates the specific data returned (bio, counts, likes, video count, verification, links). It is distinct from siblings like instagram_profile by explicitly naming TikTok, so an agent can distinguish it without ambiguity.

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 usage is implied by the description: use it when you need TikTok profile data. However, it does not explicitly contrast with alternatives such as instagram_profile or mention conditions when this tool is not appropriate. No when-not guidance is provided, so it falls at the 'implied usage' level.

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