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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds 'This is a safe, read-only tool' and mentions the performance optimization via the fields parameter, which adds a bit of context. However, it largely repeats the read-only annotation without disclosing any new behavioral traits like rate limits or authentication requirements, so the added value is modest.

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 well-structured and front-loaded with the core purpose. It uses concise sentences and includes necessary usage details without excessive verbosity. The inclusion of a fields list is informative but slightly lengthy; however, it earns its place by guiding parameter selection. Overall, it is efficient and easy to parse.

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 single-user lookup tool with no output schema, the description provides adequate context. It explicitly states the return type ('single user profile') and, combined with the schema's fields description, gives enough detail for an agent to request specific fields. It does not cover error cases or rate limits, but given the simple read-only nature and existing annotations, the description is sufficiently complete for correct invocation.

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?

The description adds meaning beyond the schema by explaining the identifierType parameter ('Use identifierType="id" for numeric user ID, identifierType="username" for username') and elaborating on the fields parameter with a default and a list of available fields. While schema description coverage is 67%, the description fills important gaps for the two required parameters and the performance-oriented fields parameter, making it more actionable than schema alone.

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 clear verb and resource: 'Get Tiktok user profile by ID or username.' It also distinguishes itself from the sibling searchTiktokUsers by clarifying that it is for exact identifiers, not fuzzy search. This makes the purpose unambiguous and differentiates it from related tools.

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 explicitly specifies when to use it: 'Use identifierType="id" for numeric user ID' and 'Use ONLY when you have the precise username.' It also gives an exclusion: 'For person names or fuzzy search, use searchTiktokUsers instead.' This provides clear, actionable guidance and names the alternative tool.

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