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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructiveness. The description adds the concrete guarantee that no private endpoints are called and that the result includes a readiness score, issues, and fixes, enriching the behavioral picture without contradicting 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?

Two tightly written sentences: the first states purpose and scope, the second states inputs and outputs. Every word earns its place, and the most important information (read-only, public URL) is front-loaded.

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?

With an output schema present, the description sufficiently covers what the tool does, what it accepts, and what it returns (score, issues, fixes). The sibling context and annotations fill in remaining gaps, but the description itself doesn't explicitly address alternative use cases or edge conditions, so it's strong yet not maximal.

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 input schema already provides 100% description coverage for all three parameters. The description simply lists the parameter names (url, marketplace_url, expected_resources) and doesn't add new semantics beyond what the schema offers, so the baseline score 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 opens with a specific verb ('scan') and resource ('public API/provider URL'), and enumerates the metadata types scanned (x402, OpenAPI, pricing, agent-discovery). This clearly distinguishes it from sibling tools like probe_x402_paid_path, making the tool's purpose unmistakable.

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 states the tool is for read-only scanning of public URLs and explicitly notes no private endpoints are called, which gives clear context for when to use it. However, it does not name alternative tools or provide explicit 'when not to use' guidance, so it falls just short of the top score.

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