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

Annotations already indicate a safe read-only, idempotent operation, and the description adds significant context beyond that: it names the data source (EUR-Lex Cellar from the EU Publications Office), confirms no authentication is required/open access, and explicitly documents the found=false behavior for nonexistent CELEX numbers.

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 description is dense but efficient: it front-loads the core purpose, lists return fields, provides concrete CELEX examples, documents a failure mode, and identifies the source. Every sentence adds useful information without redundancy.

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 a single required parameter, detailed schema coverage, an output schema, and annotations covering safety characteristics, the description covers everything else an agent needs: expected fields, source authority, auth requirements, and the not-found response behavior.

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 the schema's celex parameter already includes format, examples, and the sector/type letter explanation. The description largely repeats this information rather than adding new parameter meaning, so the high-coverage baseline of 3 is appropriate.

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 ('Retrieve'), a specific resource ('full metadata for a specific EU legal act'), and a specific identifier ('CELEX number'). It clearly differentiates this detail tool from the sibling search, recent, and by_type tools by focusing on retrieving an individual act by its CELEX number.

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?

The first sentence makes clear this tool is for retrieving a specific known CELEX number, which strongly implies 'use when you already have the CELEX and need full metadata.' It does not explicitly mention alternatives like eurlex.legislation.search or eurlex.legislation.recent, but the context and sibling list make the intended use clear enough.

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