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

Annotations already cover readOnly/idempotent/closed-world, so the bar is lower. The description adds non-obvious context the annotations cannot: the pricing tier ('Priced at the organisation tier') and that letters are generated from the organisation's own declared circumstances rather than a shared template. It does not describe pagination or response shape, hence not a 5.

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 legal-framework list (Education Act, SEND, Care Act, Housing Act, PSED, NHS Complaints Regs, Children Act, HRA) is long enumeration that consumes most of the text, while the genuinely decisive usage condition — organisation vs. individual — is buried in the final sentence. Front-loading that condition would have earned more.

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 no parameters and no output schema, the description carries the burden of explaining what the tool is for, and it does so adequately: domain, audience, pricing tier, and the directing condition. It could say more about the shape of the returned details, but nothing essential is missing.

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; baseline 4 applies. Schema coverage is reported at 100%, and no parameter semantics are owed.

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 a specific verb (describes) and resource (StatutoryLetters' organisational letter generator), and its scope is distinguishable from siblings like get_letter_type and list_letter_types. It is clear what domain content is being fetched, though what the 'details' actually contain is described only indirectly.

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?

Explicitly states the selecting condition: 'Use this when the person asking is an organisation sending the letter, rather than an individual complaining to one.' That is a real when-to-use rule, but it does not name a sibling alternative (e.g. get_letter_type) for the individual case, so routing is left partly inferential.

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