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

No annotations are provided, so the description carries the burden. It discloses that the call is free ('Free to call') and that the output includes credit costs, giving useful behavioral context. It also states it returns 'every route', indicating the scope. It does not mention potential response size or pagination, but for a listing tool this is a reasonable level of transparency. The description adds value beyond the raw schema.

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 three sentences with no filler. The core purpose is front-loaded, then usage guidance and filters follow. Every sentence contributes: what it is, when to use it, and how to filter. It is concise yet thorough, earning its length.

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?

The tool has two optional parameters, no output schema, and no annotations. The description covers the key aspects an agent needs: what the tool does, when to use it (for uncovered routes), the two filters, and the next step (call_route). It does not describe the response format, but since there is no output schema, that might be a gap; however, the purpose and usage are clear enough for an agent to invoke it successfully. Slightly more detail on return shape would push it to a 5.

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 0% for the two optional parameters, so the description must compensate. It explains that 'platform' filters by platform and 'contains' matches on the path, adding meaning that the schema lacks. It doesn't enumerate allowed platforms or give examples, but it gives enough semantic clarity for an agent to use the filters correctly.

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 states the tool's purpose: lists every route Fetchwire serves with credit costs. It uses a specific verb 'list' and resource 'routes', and differentiates from siblings by explicitly noting it covers routes that operation tools do not (TikTok shop/live/trending, Reddit subreddits/feeds, etc.) and names the follow-up tool call_route. This makes it unmistakable which tool is which.

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?

It explicitly says to use it to find routes not covered by operation tools, and instructs to fetch one with call_route. It also mentions filtering by platform or contains. However, it does not explicitly contrast with list_platforms or state when not to use it, though the 'operation tools do not cover' phrase implies the division of labor. Good guidance overall, but could be more explicit about alternatives.

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