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

The description discloses key behaviors: output includes up/down, HTTP status, class, reachability reason, final URL, responseMs, and a signed receipt. It clarifies that the verdict is deterministic while responseMs is telemetry. With no annotations, this provides adequate transparency.

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, information-dense sentence followed by a succinct note on determinism and pricing. Every word adds value, with no redundancy or clutter.

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 simple input schema and no output schema, the description covers the essential output fields and behavioral nuances (signed receipt, determinism). Minor gaps exist (e.g., error handling, timeout behavior), but overall it is sufficiently complete for an agent to use the 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?

The input schema has 100% coverage for the 'url' parameter, and the description adds significant context about how the URL is used (probing availability, returning signed evidence), beyond the schema's minimal description.

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 function: probing URL availability and providing signed evidence. It uses specific verbs like 'probe' and lists output fields (up/down, HTTP status, etc.), distinguishing it from siblings like 'fetch' or 'headers' that don't offer signed receipts.

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 provides usage guidance by mentioning the deterministic verdict, keyless operation, and pricing, implying when to use it (for provable SLA evidence). However, it lacks explicit comparisons to alternative tools like 'fetch' or 'redirect' for availability checks.

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