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

Annotations declare readOnlyHint=true, and the description reinforces this by stating it is 'not an LLM call, always instant, never consumes archive or LLM credit' — adding meaningful behavioral context (fast, cost-free, deterministic) beyond what annotations already provide. It doesn't describe output format, but an output schema exists to cover that.

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 well-structured single paragraph with strong front-loading (purpose first) and concrete examples embedded. It is informative and relatively compact given the asset-heavy sibling set. Slightly long overall but every sentence earns its place; could be trimmed modestly.

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 a single parameter, 100% schema coverage, an output schema present, and readOnlyHint annotation, the description is quite complete. It covers what the tool does, how to phrase the goal, and when to use it. The only minor gap is not describing the exact shape of the returned routing result, but the output schema presumably handles this.

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?

Schema coverage is 100%, so the single 'goal' parameter is well-documented in the schema. The description adds value by giving concrete example goal phrases, which clarifies expected input format beyond the schema's generic 'Plain-English description.' However, this is marginal enrichment over an already-complete schema, so baseline 3 is appropriate.

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?

Description states a specific verb+resource: it is a 'deterministic tool-routing lookup' that returns which tool to call. It explicitly positions itself against the huge sibling set (routing/guidance) and even names examples (palette_specify vs interior_specify vs house_specify). The purpose is unmistakable and distinct from all siblings.

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?

Gives explicit when-to-use guidance: 'Use this before guessing between similarly-named tools' with concrete example pairs. It also gives clear usage examples of what goal phrases look like ('I have a brand colour...', 'I want to paint a whole house'). This is effectively explicit alternatives + context guidance.

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