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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds that the tool returns a catalog and input schemas, which is useful but does not disclose additional behavioral traits such as authentication requirements, rate limits, or what happens if the paid catalog is empty. With annotations already covering safety, a score of 3 is appropriate.

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 description is a single, well-structured sentence that front-loads the core action ('Find the paid API catalog and buying instructions') and then lists additional outputs. There is no filler or redundant wording, making it highly concise without loss of meaning.

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?

Given that the tool has no parameters, annotations cover safety traits, and there is no output schema, the description sufficiently states what the tool returns. It could mention a prerequisite (e.g., authentication required to access the catalog) but for a discovery tool with no inputs, this is a minor omission. The tool is otherwise complete for an agent to call 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?

The tool has zero parameters, so there is nothing to explain. Per the rubric, a tool with 0 parameters receives a baseline of 4. The description adds no parameter information, which is expected and adequate.

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?

The description clearly states the tool's purpose: it finds the paid API catalog, buying instructions, provider operations, and input schemas. It specifies a concrete resource and what it returns, but it does not explicitly differentiate this discovery tool from the sibling tools (e.g., xguard_execute, xguard_quote), which is a minor gap in clarity.

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?

The description gives no guidance on when to use this tool versus alternatives. It does not say whether to use this before calling other tools, or to discover what APIs are available. The absence of usage context or routing instructions leaves the agent to infer when xguard_discover is the right choice among its many siblings.

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