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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), but the description adds substantial value by disclosing what comes back: rule lines with sources and seen levels, makers' declarations flagged as such, NEC listing ladders, or a not_found with a stated reason. That is valuable because there is no output schema. 'Free, deterministic, no LLM' also sets cost/latency expectations.

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 with no filler, but the first is overloaded: a nine-item parenthetical and a seven-country list duplicate the enum values already in the schema. The genuinely useful part (return shape, not_found behavior) is stacked behind that enumeration instead of being front-loaded.

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 two-required-enum lookup with no output schema, the description does the necessary work by explaining the returned payload and the not_found outcome, and by routing the decoding case to a sibling. It does not address behavior for a country/place combination outside the supported rules set beyond the generic not_found note.

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 all three parameters are enums with documented values, so the schema already carries the semantics. The description restates the same place list and country list but adds no format, default, or edge-case guidance beyond what the schema provides, so the baseline 3 applies.

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 identifies a specific resource (the lowest fire class or listing a country requires) and the scoping dimensions (country set, nine building/space types), and explicitly differentiates itself from decode_cable_code. It falls short of 5 because the purpose is delivered as a long noun phrase rather than a crisp verb-first statement, so the core action is somewhat buried.

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?

It states the use case directly ('Use it to choose the fire class to ask for') and names the alternative plus the condition that selects it ('to read the class a designation prints use decode_cable_code (cpr_printed)'). No explicit when-not guidance is given beyond that split, which keeps it from a 5.

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