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

With readOnlyHint, idempotentHint, and destructiveHint=false already provided, the description adds specific behavioral context by enumerating the no-operations (no-execution, no-spend, etc.), which clarifies the safety profile beyond generic hints. It aligns with annotations and enhances understanding of the tool's non-mutating nature.

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, concise sentence that is front-loaded with the verb and directly states the tool's scope. Every word contributes to the meaning, with no filler or redundancy.

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?

This is a simple, no-parameter explanation tool. The description fully conveys the tool's purpose and behavior. While there is no output schema, the act of 'explaining' implies a textual answer, and the description is sufficient for a low-complexity tool.

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 the baseline is 4. The description does not need to explain parameter semantics, and the empty schema covers all parameters with 100% coverage. No additional parameter information is required.

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 uses a specific verb 'Explain' and clearly identifies the resource: the boundary for external marketplace search, listing four precise constraints (no-execution, no-spend, no-settlement, no-trust-mutation). This distinguishes it from sibling tools that actually perform marketplace operations or searches.

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 implies that this tool is for understanding the boundaries of external marketplace search, but it does not explicitly state when to use this tool over alternatives, nor does it mention exclusions or when not to use it. The context is only implied by the nature of the explanation.

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