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

With no annotations, the description carries the full behavioral burden and does a solid job: it discloses the flat credit cost, that empty results and failures are never charged, and the cache=true behavior with a 24h window and default fresh fetch. This goes beyond simple operation descriptions and gives the agent useful cost/retry expectations, though it does not cover rate limits or error formats.

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 core purpose before behavior details. However, 'Flat 1 credit. Costs 1 credit.' is redundant, which prevents a perfect score for zero-waste structure.

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 three-parameter tool with no output schema, the description gives enough context: purpose, output fields, pricing, failure charging, and cache semantics. It does not explain the limit parameter's default/max, but the schema covers that, so the omission is acceptable.

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 the baseline is 3. The description does not add meaning beyond what the schema already documents for q, cache, or limit; it references cache behavior but repeats the schema's own description. No additional parameter guidance is provided.

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 states a precise verb and resource: 'Threads user discovery from keyword search'. It also enumerates the returned fields (id, handle, avatar, verified), which makes the tool's purpose unmistakable and distinguishes it from sibling tools like 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?

The description clearly frames the tool as the one for discovering Threads users via keyword search, giving an agent clear context for when to pick it. It does not explicitly name alternatives or exclusions, but the purpose phrasing alone is enough to route correctly among many search siblings.

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