Get Users By IDs

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open world), and the description goes well beyond them: it discloses the API key requirement, one request per call, an approximate cost of 1 unit, and that per-result cost estimates are returned. It also explains the partial-failure behavior via completeness.notReturned, which is exactly the kind of behavioral detail an agent cannot infer from 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?

Four tight sentences: purpose and limit first, then the partial-result note, then the sibling routing, then operational constraints. Every sentence carries information, though the cost clause is slightly dense and could be split for faster 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?

An output schema exists, so return-shape explanation is not owed, and the description still adds auth, cost, and partial-result semantics for a batched read tool. The only real gap is guidance on when to choose responseFormat=compact, which is left entirely to the schema.

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 both userIds and responseFormat are already documented in the schema, including the enum semantics and the 100-item cap. The description's 'up to 100 ... numeric user ID' restates schema content and says nothing about responseFormat, so the baseline 3 applies.

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 and resource ('Fetch ... public user profiles ... by numeric user ID') plus a concrete scope cap of 100 per call. That distinguishes it clearly from the single-record sibling tweetapi_user_by_id and from the username-based siblings.

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?

Explicitly routes username-based lookups to tweetapi_user_by_usernames, which is the most likely confusion point in a family with ~45 user tools. It stops short of saying when not to use it or contrasting with the singular tweetapi_user_by_id, so it is strong rather than exhaustive guidance.

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