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

Annotations already establish read-only, idempotent, non-destructive behavior, yet the description still adds substantial non-obvious traits: silent truncation past 100 ids, missing ids absent with no error row, unordered results, per-row billing, and an untrusted-content warning. These are behavioral facts the structured fields cannot convey.

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?

Dense, front-loaded prose where every clause carries distinct information (routing, cap behavior, return shape, error semantics, ordering, billing, safety). No filler or restatement of the name.

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 naming the returned fields (pk, username, full_name, is_verified, follower_count, media_count) and the error/ordering behavior. An agent has everything needed to call and interpret this tool.

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%, so baseline is 3, but the description adds real meaning beyond it: `limit` caps both returned rows and cost (billing semantics not in the schema), and it reinforces why ids are strings. That is value beyond the schema text, though the parameter list is short.

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+resource and scope ('Get up to 100 TikTok user profiles by pk in a single call') and explicitly distinguishes itself from the singular sibling get_tt_user_by_id. An agent can route between the two without opening either 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?

Gives an explicit when-to-use rule ('use it instead of repeated get_tt_user_by_id calls') plus the operative constraint (hard-capped at 100, extras silently dropped). This is exactly the routing information needed versus the many sibling lookup tools.

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