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

With no annotations, the description carries the full behavioral burden. It discloses that the tool is free, that ratings are 'based on what Mizan measured' (so they are empirical, not speculative), and enumerates the possible return values. This is meaningful behavioral information beyond a mere 'check' label.

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 short sentences, no filler. The first sentence contains the core purpose, output values, and data source; the second gives the temporal use case. Every word earns its place.

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?

Although there is no output schema, the description explicitly lists the possible return values ('avoid / caution / ok / unrated'), so an agent knows what to expect. It lacks discussion of error cases or edge conditions, but for a simple rating tool this is sufficient and complete enough for an agent to call and use the result.

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 has 100% description coverage for both 'url' and 'host', so the schema already explains the parameters clearly. The description adds no additional parameter semantics beyond mapping 'endpoint' to 'url' and 'operator' to 'host' – which is already implied by the schema descriptions. Baseline 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 states a specific action ('Returns avoid / caution / ok / unrated') for a clear resource ('an x402 endpoint or operator') and even describes the basis ('what Mizan measured... with its own money'). It clearly distinguishes this as a rating/check tool from siblings like mizan_coverage or mizan_report without needing to inspect them.

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?

Provides an explicit use case instruction: 'Call this before any x402 payment.' This tells an agent exactly when to invoke the tool. It does not mention alternatives or exclusions, but the timing instruction is strong and unambiguous.

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