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

Annotations already indicate readOnlyHint=true and openWorldHint=true, so the description's contribution is the API key requirement and the clarification that it returns a URL rather than the actual text. This adds value beyond annotations without contradicting them.

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 front-loaded with the core purpose in the first sentence, followed by usage context, a requirement, and parameter explanations. Every sentence contributes value without redundancy or 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?

For a simple tool with two parameters and an output schema, the description covers purpose, usage, auth requirement, and parameter semantics. The existence of an output schema means return value details are not necessary, and the description sufficiently communicates the tool's scope.

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?

With 0% schema description coverage, the description fully compensates by explaining both parameters: query is described with an example ('data processing agreement processor obligations') and regulation as an optional scope example ('gdpr'). This provides meaningful semantics beyond the bare property names.

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 clearly states the tool's purpose: 'Return EUR-Lex search URL for finding regulation provisions by keyword.' This is a specific verb+resource combination. It also distinguishes from siblings by mentioning 'when you don't know the exact article number,' implying an alternative for article lookup.

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 description provides an explicit usage trigger: 'Use when you don't know the exact article number but need to find relevant provisions.' It also mentions the Velvoite Premium API key requirement, but does not explicitly name alternative tools like get_eu_regulation_article, so it lacks full alternative guidance.

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