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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and openness are covered. The description usefully adds that results are limited to public accounts and that the call costs 1 credit, but it does not describe return shape, pagination, or caching behavior.

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 short sentences, front-loaded with purpose and scope, with no filler. Every sentence adds a distinct fact: action, scope, and cost.

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 simple search tool this covers the core purpose and cost, but it leaves meaningful gaps for an agent navigating many sibling tools. It lacks routing guidance versus threads_search and threads_profile, and it does not explain the undocumented cache_max_age parameter.

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 required query parameter is already documented in the schema as 'Keyword or partial handle', and the description only restates the keyword idea without adding syntax or matching behavior. The second parameter, cache_max_age, is undocumented in both the schema and the description, leaving half the parameters unexplained.

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 ('Search users') and scopes it to public Threads accounts matching a keyword. It is clear on its own, but it does not distinguish itself from nearby siblings such as threads_search or threads_profile.

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?

There is no explicit when-to-use guidance, no when-not-to-use guidance, and no named alternatives. The agent must infer that this is for user discovery rather than generic Threads search or profile lookup.

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