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

The annotations already cover safety-related behavior (readOnlyHint, openWorldHint, idempotentHint, non-destructive). The description adds valuable context by specifying the legal scope, available filters, and the exact returned fields. It does not contradict the annotations and adds enough behavioral context beyond the schema.

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 well-structured: it states the resource and legal scope first, then filters, then returns, then example use cases. Each sentence carries distinct information and there is no filler or repetition of schema content.

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 23-parameter search tool, the schema covers all parameter semantics and no parameters are required, while the description provides the data domain and result fields. There is no output schema, but the description names the main return fields. Minor gaps such as default sorting or behavior with no filters are left to the schema, but nothing critical 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?

Schema description coverage is 100%, and each parameter already has a meaningful description. The tool description only lists broad filter categories without adding syntax, value constraints, or cross-parameter semantics. This matches the baseline of 3 for high schema coverage.

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 uses a specific verb ('search clinical trials in the EU/EEA under Regulation 536/2014') and names a clear resource: the EU Clinical Trials Information System. It also enumerates filter dimensions and returned fields, so an agent understands what the tool does. However, it never explicitly contrasts itself with sibling tools like ctis_trials_for_medicine or ctis_trial, so sibling differentiation is only implicit.

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 gives clear usage context through the final sentence: it answers questions about which European trials are recruiting, who sponsors them, and which member states they run in. It does not explicitly state when not to use this tool or point to a sibling alternative, which keeps it a step short of full guidance.

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