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

Annotations already provide readOnlyHint, idempotentHint, and destructiveHint=false, covering safety. The description adds valuable context beyond annotations: 'Returns the in-bundle catalog; no upstream call; no isError path.' This informs the agent about the tool's execution model and error behavior, although it isn't a full behavioral contract.

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 sentences, front-loaded with the core purpose, followed by usage guidance and behavioral notes. Every sentence earns its place; no fluff or repetition. The structure is ideal for quick comprehension.

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 zero-parameter, read-only list tool with an output schema, the description fully covers purpose, use case, and execution traits. The presence of an output schema eliminates the need to describe return fields, and the description confirms the tool is safe and self-contained. It is complete for the tool's simplicity.

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 description cannot add parameter-level meaning. Per guidelines, a no-parameter tool receives a baseline of 4. The description's mention of '9 canonical service slugs' is an output detail rather than a parameter semantic, but it gives a sense of the result size.

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 a specific verb and resource: 'List the 9 canonical valet service slugs with display name and category.' It distinguishes itself from sibling tools by focusing on the service taxonomy, while siblings handle operators and cities. The 9-slug detail is concrete and unambiguous.

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 states when to use: 'Use this when an agent needs to validate or discover the supported service taxonomy before composing a follow-up search.' It even names a sibling tool as a companion, showing awareness of alternatives. Clarifies that no upstream call occurs, which sets expectations for reliability and speed.

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