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

Annotations already cover read-only, non-destructive, open-world, and non-idempotent, so the safety profile is settled; the description adds that the vocabulary is 'live' (explaining the non-idempotent hint) and that each value carries a vacancy count plus numeric ranges. That return-shape information is genuinely useful because there is no output schema. It does not mention size, cost, or the circular note that the `filters` argument expects values produced by this same tool.

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 what the tool returns, then the imperative usage rule and the skill-slug caveat. No filler, no restated title, nothing that could be cut without losing information.

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-required-parameter discovery tool this is largely callable as-is, and the description covers purpose, timing, and rough return shape. What is missing is differentiation from 'list_filter_values' and any explanation of how to use the 34-key `filters` slice, which is the only real complexity in the definition.

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 description coverage is 100% and there is a single optional nested `filters` object, so the baseline is 3. The description says nothing about narrowing the vocabulary or what happens to counts when a slice is applied; the schema's own note ('Each value is a list of values from the facets tool') is self-referential and the description does not clarify it.

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 and resource ('List the live filter vocabulary: every filter's valid values with a vacancy count each, plus numeric ranges'), which is far more than a restatement of the title. An agent knows exactly what comes back: per-value counts and numeric ranges. It stops short of a 5 because the near-identical sibling 'list_filter_values' is never mentioned, leaving ambiguity about which of the two to call.

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?

Explicit sequencing guidance is given ('Call this BEFORE filtering a search'), plus a hard constraint ('never invent a filter value'), which is exactly the failure mode this tool prevents. No exclusions or when-not-to-use guidance is provided, and it does not route the agent away from the sibling 'list_filter_values'.

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