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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the enumeration is complete ('Every ODS role code') and there is a cost model (free within the daily allowance, then $0.0005 USDC per call via x402), which is material for an agent deciding whether to invoke.

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 tight sentences: the first front-loads what the tool returns, the second front-loads the cost condition. Every clause earns its place with no filler.

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?

With an output schema present, return values need not be explained, and with zero parameters there is no schema gap to fill. Annotations cover safety, and the description covers scope and pricing; only minor omissions (e.g. whether the code list is versioned or how often it changes) keep it from a 5.

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 the baseline is 4; there is nothing for the description to disambiguate. The reference to aliases that 'search accepts' adds a small amount of interpretive value about how the returned data is consumed, but no parameter semantics exist to document.

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?

States a specific resource ('Every ODS role code with its name') and the added value (friendly aliases accepted by search), so an agent knows this is a static reference/enumeration lookup rather than a filtered query. It does not explicitly name sibling tools like nhs-organisations__search to differentiate, keeping it short of a 5.

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?

Usage is only implied: the mention of 'the friendly aliases search accepts' hints this is the companion lookup for resolving role codes before calling search, but there is no explicit when-to-use or when-not-to-use statement and no named alternative. Pricing terms are given, but that is not selection guidance.

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