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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered elsewhere. The description adds the useful facts that these are test resources and that prices/tags are returned, but says nothing about result volume, ordering, or behavior when the tag matches nothing.

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?

Two short sentences, front-loaded with the capability and followed by the selection cue. Nothing is wasted and no sentence is 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?

For a one-parameter, read-only list tool with no output schema, the description covers what it returns (prices, tags) and when to call it, which is sufficient to invoke correctly. Minor gaps are result ordering/empty-result behavior rather than blocking omissions.

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?

There is a single optional parameter with 100% schema description coverage ('Resource tag to filter by'), so the schema carries the semantics. The description's 'optionally filter by tag' confirms optionality but adds no matching rules or format details beyond the schema — baseline 3.

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 ('List') and a specific resource ('cp0x's x402 test resources') plus what each entry carries (listed prices and tags). It doesn't explicitly distinguish itself from the nearby sibling list_x402_facilitators, but the resource nouns differ enough that an agent can infer the split.

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?

'Use this when the user asks about x402 resources or pay-per-call APIs' gives a clear triggering context. It stops short of naming an alternative (e.g., list_x402_facilitators) or stating when not to use it, so it lands at 4 rather than 5.

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