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

With no annotations provided, the description carries the full behavioral burden. It discloses flat pricing, the fact that empty results and failures are never charged, and the cache behavior. This adds meaningful operational context beyond the schema, though it does not mention rate limits or return format.

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 purpose is front-loaded and the description is short, but 'Flat 2 credits. Costs 2 credits.' is redundant, and 'default always fresh' is already present in the cache parameter schema. Minor wasted words prevent a higher score.

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 with three well-documented parameters and no nested objects, the description provides sufficient context: what it searches, what kind of results it returns, cost, failure charging, and cache behavior. The main gap is the lack of explicit sibling-tool routing, but the tool itself is adequately specified.

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 schema already documents q, cache, and limit clearly. The description mostly repeats cost and cache behavior rather than adding new parameter-level meaning. The baseline 3 is appropriate here.

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 names a specific verb and resource: 'keyword search' over 'Threads posts'. It also characterizes the result as 'posts with engagement + media', which helps distinguish it from user/profile searches like threads_search_users. However, it does not explicitly name sibling alternatives, so it stops just short of a 5.

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 guidance on when to use this tool versus alternatives such as threads_search_users, threads_post_details, or threads_user_posts. The phrase 'posts with engagement + media' gives an implied hint, but no when-to-use or when-not-to-use conditions are stated.

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