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

With no annotations provided, the description must carry the behavioral disclosure burden, and it does so well. It discloses the cost of 1 credit, that empty results and failures are never charged, and that cache=true provides a free 24-hour hit while the default is always fresh. This gives the agent a clear picture of side effects and resource usage beyond the schema. It does not mention rate limits or authentication, but the most relevant behavioral traits are covered.

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 compact and front-loaded with the tool's purpose and key returned fields. It packs cost, failure policy, and cache behavior into a short text. Minor redundancy exists between "HD avatars (1 credit)" and "Costs 1 credit," but overall every sentence earns its place.

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?

Given there is no output schema, the description compensates by listing the main response fields, which helps the agent know what to expect. It also covers cost, cache, and failure handling. It does not fully describe response shape or error cases, but for a simple profile-lookup tool with only two well-documented parameters, the description is reasonably complete.

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 the baseline is 3 because the schema already documents both parameters thoroughly. The description does not add semantic value for the url parameter beyond what the schema says, and the cache explanation in the description largely duplicates the schema's cache description. No credit is lost, but no additional parameter insight is provided either.

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 clearly identifies the tool as a Threads profile fetch and enumerates the specific fields returned (displayName, privacy, bioLinks, avatars). It does not use an explicit verb like "fetch" or "get," but the resource and output are unmistakable. It differentiates from sibling tools like threads_user_posts or threads_search because it targets a single profile rather than posts or search results.

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 provides practical usage details such as credit cost, no charge on empty/failed results, and cache behavior. It also implicitly tells users when to use this tool: when they need a single Threads profile's metadata. However, it does not explicitly contrast it with alternatives like threads_search_users or threads_user_posts, nor does it state exclusions or when not to use it.

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