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

Goes well past the annotations by disclosing cost ($0.01 USDC per call), the x402 payment location in _meta["x402/payment"], and the exact non-charge conditions (unknown vendor, invalid input, upstream failure). The read-only hint is restated but the billing semantics are new and decision-critical.

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 capability and fields come first, then routing to alternatives, then cost rules — a well front-loaded order with no filler. It is dense (four sentences plus parentheticals) but each sentence carries a distinct operational fact.

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?

No output schema, yet the description enumerates the returned signals and their freshness, so an agent knows what it gets for its money. Combined with the payment and error semantics, nothing needed to call this correctly is missing.

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 coverage is 100% and the schema already documents the accepted name/slug/domain forms, so the baseline is 3. The description earns an extra point by specifying the consequence of a bad value: unknown vendors return an error and are not charged, which affects how an agent should validate before calling.

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?

Specific verb and resource ('check whether one SaaS or cloud vendor is down right now') plus the exact payload fields returned (status, confidence, incidents, uptime, freshness). Explicitly scoped to a single vendor, which separates it cleanly from multi_vendor_status.

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?

States the selection rule directly: use this for one vendor, use multi_vendor_status for up to 25. Adds a prerequisite route via the free list_vendors for uncertain names. Nothing is left to inference.

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