well_known_capabilities

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context by specifying the document is signed with RS256 (a verifiable trust anchor), but it says nothing about whether the endpoint is public or needs auth, or how the signature should be validated.

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?

A single front-loaded sentence that identifies the resource and its key property (signed RS256). No filler, no redundancy with the title.

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 exists, so the description carries the return-value burden; it names the artifact but not what the capability document contains or how to consume the signature. For a simple discovery endpoint this is borderline adequate, but an agent gains little actionable detail about the payload.

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 tool takes zero parameters and the schema is an empty object, so there is no parameter semantics to explain. Per the baseline for 0-param tools, a 4 is appropriate; the description correctly implies no inputs are needed.

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 ('Return') and a well-defined resource ('signed RS256 capability document for this Seller MCP Node'), which is clearly distinct from transactional siblings like create_intent or check_availability. It does not explicitly name or contrast with siblings, but the resource is unique enough that confusion is unlikely.

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?

There is no indication of when an agent should call this versus discover_products or the other siblings, nor any prerequisites or call ordering. The well-known/trust-anchor nature implies a discovery/bootstrap use, but that must be inferred entirely by the reader.

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