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

Annotations already declare read-only, idempotent, non-destructive and open-world, but the description adds material behavior they cannot express: a $0.01 USDC per-call charge via x402 with the payment passed in _meta["x402/payment"], and the billing exemptions for invalid input or upstream failure. That is precisely the kind of cost/auth context annotations cannot carry.

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 dense sentences, front-loaded with what is returned, then the sibling route, then the prerequisite and billing mechanics. Every clause carries actionable information; nothing is redundant with the schema or annotations.

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 no output schema, the description compensates by enumerating the response contents (status, confidence, incidents, 30-day uptime, data freshness). Payment flow, prerequisite lookup and error billing behavior round out what an agent needs to call this correctly.

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% and the single vendor parameter already documents accepted forms ('Stripe', 'stripe', stripe.com). The description implies a single-vendor scope but adds no format or validation detail 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?

States a specific verb (check) and resource (one SaaS/cloud vendor's current status), enumerates the returned signals, and explicitly names the sibling it is not (multi_vendor_status). An agent can distinguish it from multi_vendor_status, list_vendors and validate_vendor without opening any schema.

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?

Gives explicit routing rules: use this for one vendor, multi_vendor_status for up to 25, call list_vendors (free) first if the vendor's tracking status is unknown. It also discloses the failure mode (unknown vendors error and are not charged), which is a usage-relevant exclusion.

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