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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety profile is covered. The description still adds useful operational context: it is free, read-only, filtered to incident-free endpoints, and rankings refresh as monitoring runs every 30 minutes. It does not describe ordering/pagination behavior beyond 'best first', so it stops short of a 5.

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 sentences, each earning its place: the first defines the resource and output, the second gives the use case, the third handles routing, cost and freshness. The scoping and routing information is front-loaded with no filler.

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?

An output schema exists, so return values need no explanation. The description covers selection criteria, ordering, freshness cadence, cost, safety profile and sibling routing — everything 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% with a single optional 'limit' parameter (1-50, default 10), so the schema already documents the parameter fully. The description adds nothing about how limit interacts with ranking or whether truncation occurs, 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 and resource ('List the x402 endpoints that are currently safest to pay') with the exact filter criteria (verdict proceed or caution, no payout-wallet incidents) and returns score, grade, verdict and test-payment status. It clearly distinguishes itself from check_endpoint and check_payment by naming both siblings.

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?

Explicitly says when to use this tool ('discover reliable endpoints or pick between providers') and routes to alternatives for the two adjacent cases: check_endpoint for evaluating one endpoint and check_payment for approving a payment. No inference is required.

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