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

With no annotations, the description carries full burden. It clarifies the result is 'Evidence only' and not a payable proof, which is useful context, but omits whether it is read-only (implied but unstated), whether results are paginated beyond the 20 cap, or what 'index row' means operationally.

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?

Three terse sentences with no filler. The caveats are front-loaded after the core statement, though the telegraphic style borders on cryptic.

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 tool with no annotations and no output schema, the description should explain the return shape (list of hosts, ordering) and confirm read-only nature. It leaves key operational details to inference, which is risky given the absence of structured metadata.

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%; the schema fully documents the optional query parameter, its case-insensitivity, substring behavior, and the 20-result cap. The description adds no parameter-specific meaning beyond the schema, so baseline 3 applies.

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 name 'find_payable' and description 'Alphabetical hosts whose index row includes x402' suggest it retrieves a list of hosts referencing x402, but the phrasing is indirect and jargon-heavy. 'x402' is unexplained, and the tool's relationship to siblings like lookup_host or payto_check is unclear. The purpose is ascertainable but not crisply stated.

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 offers no guidance on when to use this tool versus alternatives such as lookup_host or list_changes. The caveat 'Not a rank and not a payable proof' hints at scope but doesn't state when to prefer this over other discovery tools.

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