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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is fully covered without prose. The only behavioral fact the description adds — the 100-user batch limit — is already encoded in the schema (maxItems: 100), so the description contributes essentially nothing beyond structured data, though it does not contradict it.

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?

A single front-loaded sentence with zero filler; the batch scope and the ID-keying requirement appear before anything else. Nothing in it is redundant or padded.

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?

There is no output schema, so the description is the only place to learn what a 'profile' contains, and it says nothing about the returned fields, response ordering, or missing/suspended user handling. Combined with the untouched format and max_chars behaviors, it is adequate but leaves real gaps for an agent shaping a batch lookup.

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%, including detail on the format enum (simple vs raw and their token trade-offs) and the max_chars truncation behavior, so the schema does the heavy lifting. The description only restates 'numeric user ID' and the 100-item ceiling, adding no syntax or format guidance of its own — the correct baseline 3.

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 ('Get profiles for ... X users'), plus the batch scope ('up to 100 ... in one call') and the keying method ('numeric user ID'). This implicitly separates it from get_user_by_id (single), get_user_by_username and username_to_id, but never names those siblings explicitly.

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?

Batch intent is implied by 'up to 100 X users in one call', so an agent can infer this for multi-user lookups. However, there is no explicit routing guidance such as 'use get_user_by_id for a single user' or 'use username_to_id first if you have handles, not IDs', which is exactly the ambiguity this tool's siblings create.

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