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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is known. The description adds valuable behavior beyond that: 'Browsing is free and needs no key' clarifies authentication and cost expectations, which is important for an agent deciding whether to call this tool. It doesn't explain pagination or result shape, but the bar is lower given the annotations.

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: the first gives user-centric purpose and usage, the second states return contents and access requirements. Every sentence earns its place, with no filler or repetition of schema details.

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?

There is no output schema, but the description explicitly states what is returned: 'price per call in USD and the endpoint to call it.' It also covers access (free, no key) and the scope of results (every tool). Given the three simple optional parameters and clear annotations, this is complete for a filtered-list retrieval tool.

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 input schema already fully documents all three optional parameters. The description adds no parameter-specific meaning, relying on the structured schema. This meets the baseline of 3 for high coverage but does not exceed it.

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 identifies the tool as a marketplace search for paid tools: 'Find a paid tool that does something you cannot do yourself' and specifies it 'Returns every tool on the market with its price per call in USD and the endpoint to call it.' This distinguishes it from sibling tools like get_earnings or register_server by focusing on browsing/listing external offerings.

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?

Explicit usage conditions are provided: 'Use when the user needs a capability you lack and is willing to pay per use, or asks what paid tools, APIs or data sources are available.' This directly tells the agent when to invoke this tool versus other actions like registering or pricing tools, offering clear decision guidance.

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