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

With no annotations provided, the description carries the burden of disclosing behavioral traits. It discloses that free scans are limited per client and that past the limit the response includes an upgrade link, which is valuable. However, it does not mention any error handling (e.g., invalid URL), whether the image must be publicly accessible (though the schema hints at 'public URL'), or that this is a read-only operation (though implied). It is not misleading but could be more explicit about potential failure modes and constraints.

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 two sentences with no redundancy. The first sentence states the core purpose, and the second provides the input instruction and discloses the limit. It is front-loaded with the most critical information and each sentence earns its place. No fluff or irrelevant detail.

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 tool with 2 parameters, no output schema, and no annotations, the description covers the essential context: what it does, how to invoke it (image URL), what the response includes (item identity, resale range, sell-through signals), and the free-scan limitation. It does not detail error cases or the exact format of the output, but these are not critical for a basic scan tool. The description is adequately complete for an agent to call it correctly.

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 schema description coverage is 100%, with both parameters having meaningful descriptions: category lists example hints, and image_url defines its purpose. The tool description adds no extra parameter meaning beyond what the schema already provides. It only restates that an image URL is needed, which is already in the schema. Therefore, the baseline of 3 is appropriate.

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: estimating resale value of a secondhand item from an image URL. It names the specific verb 'Estimate' and the resource ('what a secondhand item is worth to resell'), and mentions the FlipWorth vision engine. This is distinct from the sibling tools (deprecation_check, website_audit), so there is no ambiguity.

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 clear context on when to use the tool: 'thrift find, garage sale, shelf photo'. It implies the primary use case is for secondhand items with a photo available. It does not explicitly state alternatives or exclusions, but the siblings are unrelated, so this is sufficient. A clear 'use this when you have a photo of a used item' is effectively conveyed.

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