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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering safety and side effects. The description adds value by enumerating the returned fields (NCT ID, title, phases, etc.) and the exact status filter, providing behavioral detail beyond what annotations state.

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 compact (three sentences), front-loads the main purpose, and includes a source attribution. Every sentence adds useful context without redundant fluff, though the source note is slightly tangential.

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?

Given the tool's simplicity and the presence of annotations and an output schema (implied by the returned fields list), the description is sufficiently complete: it states what it returns, gives a concrete phase example, and indicates the intended user. Minor omission of explicit constraints like date ranges or pagination, but those are not critical.

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?

All 4 parameters have schema descriptions with 100% coverage, so the schema already documents their meaning. The description repeats some of this (e.g., 'condition or drug' and phase examples) but does not add significant new semantics beyond the schema, matching the baseline of 3.

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 ('Find'), a clear resource ('clinical trials currently open for enrollment'), and distinguishes it from generic search by specifying the status filter 'RECRUITING'. It also lists the key fields returned, making the tool's purpose unambiguous.

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 clearly indicates when to use this tool: for patients or researchers seeking open studies, with optional phase filtering. It does not explicitly contrast with sibling tools like 'search' or 'detail', but the 'currently open for enrollment' scoping implies the distinction. Slight gap in explicit exclusion guidance.

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