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

The readOnlyHint annotation already establishes that this is a safe read operation. The description adds context about the information returned (fixed prices, current sponsorship availability, rules), which helps set expectations but does not disclose behavioral traits like authentication requirements, rate limits, or side effects beyond the annotation.

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 a single, well-structured sentence with no wasted words. It front-loads the core purpose and efficiently lists the key content categories, making it easy to scan.

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 the simplicity of the tool (no parameters, no output schema, only a readOnlyHint), the description adequately conveys what the tool returns. It could be slightly more complete by specifying the return format or structure, but it covers the essential content.

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 tool takes no parameters, so there is no parameter schema to supplement. Per the rubric, zero parameters yield a baseline score of 4, and the description rightly does not spend words on parameters.

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 content: ways to get an API listed or sponsored, with prices, availability, and rules. It is specific enough for an agent to understand what the tool provides, though it uses a noun phrase rather than an explicit verb and does not differentiate from siblings.

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?

No explicit when-to-use guidance or mention of alternatives is given. However, the description's content strongly implies the tool should be used when an agent needs information about listing or sponsoring an API on PublicAPIs.io, making usage inferable but not spelled out.

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