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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description adds substantial context: the data comes from a database snapshot, not a live TikTok fetch; a missing user yields the literal string 'User not found'; and returned content is user-generated and should be treated as untrusted. These are meaningful behavioral disclosures beyond the structured fields.

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 sentences, all front-loaded with the essential retrieval constraint first, then sibling routing, then return shape and safety note. No filler; every clause carries distinct information.

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?

With no output schema, the description compensates by enumerating the returned profile fields (username, full_name, biography, region, language, verification/privacy flags, counts, sec_uid) and the not-found outcome. For a single-parameter, non-live lookup tool, nothing an agent needs to call 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 coverage is 100% and the single parameter is documented in the schema, so the baseline is 3. The description adds matching semantics the schema omits: the handle is matched exactly and case-insensitively, and the '@' prefix must be stripped. That meaning-over-schema pushes it above baseline.

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 (Get) and resource (one TikTok profile), plus the key scope qualifier: exact handle, case-insensitive, without @, sourced from the DataLikers database rather than a live fetch. It explicitly contrasts itself with get_tt_user_by_id and search_tt_users, so an agent can pick it apart from its many siblings without opening a schema.

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?

Provides an explicit use condition ('when you know the handle') and names three alternatives with the disambiguating condition for each: get_tt_user_by_id for a numeric pk, search_tt_users for partial names, get_user_by_username for Instagram. This is near-ideal routing guidance.

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