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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely useful non-obvious behavior beyond that: the pricing model (free within the daily allowance, then $0.0005 USDC per call via x402), which materially affects invocation decisions. It stops short of noting anything about result stability or caching.

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 short sentences with zero filler: purpose first, cost second. Nothing is redundant, though the purpose clause is so compressed that a few more words of scope would have cost nothing.

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 parameterless reference lookup with an output schema present, the description covers what the tool returns and its cost, which is enough for an agent to call it correctly. The remaining gap is workflow placement — it never says this is the tool to consult before filtering other legislation calls.

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 takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. No parameter text is needed or expected here.

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 states the resource ("Type codes and what they mean") but gives no verb and no scope statement, so it reads more like a label than an action. It is distinguishable from siblings like uk-legislation__search or uk-legislation__item only by inference, since it never says it is a static reference list of legislation types. Purpose is inferable but not crisp.

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?

There is no guidance on when to call this versus the sibling legislation tools, and no hint of the obvious use case (resolving the type codes that search/item expect). The only contextual sentence is about billing, not usage. An agent must guess the tool's role in a workflow.

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