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

Annotations already declare read-only, idempotent and non-destructive, so the bar is lower, yet the description still adds real context: unknown ids return the specific error deadline_not_found, days_until is computed against today's date, and the dataset provenance (26 obligations, 12 laws, 19 acts, earlier dates retained in history) is disclosed. The long metering paragraph also surfaces quota behavior (10 free answers/day, samples lacking history and file proof), though that text reads as generic boilerplate rather than tool-specific behavior.

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 opening two sentences are front-loaded and earn their place, as is the output inventory. However, roughly half the text is a generic free-tier/metering and sanctions-error policy that is not specific to fetching a single deadline and dilutes the key lookup guidance.

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 output schema, the description correctly compensates by enumerating the returned fields (as_of, verified, obligation, date, previous_date, status, days_until, source URL, quote, SHA-256, history) and the not-found error path, which is what an agent needs for a single-record getter. The only shortfall is that pagination/sample-truncation behavior is buried in boilerplate rather than stated as a return-value caveat.

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 coverage is 100% and the schema already carries the pattern, an example and the lookup-origin note, so the description's restatement of "required, 1 to 80 lowercase letters/digits/hyphens, case-sensitive, e.g. eudr-large-medium-operators" is largely duplication. The only added semantic value is reinforcing that the id must come verbatim from the list endpoint. Baseline 3 applies when the schema does the heavy lifting.

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 verb and resource ("Returns one statutory EU compliance deadline by its exact id") and immediately enumerates what comes back: Official Journal source, quote, SHA-256 and dated history. This is clearly distinguishable from compliance_list_deadlines, which the description itself names as the collection endpoint.

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?

Gives an explicit precondition ("when you already have an id from compliance_list_deadlines") and redirects to the sibling for the alternative case (searching by law or dates, or retrieving several at once). The agent knows which of the two tools to pick without opening a schema.

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