clinicaltrialsgov-mcp-server

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

Annotations declare readOnly/idempotent/openWorld, so safety is covered. Description adds valuable behavioral context that 'study counts per value' are included in the return data, and clarifies this is a discovery/exploration operation. Does not contradict annotations.

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?

Two sentences with zero waste. First sentence establishes core functionality; second provides usage guidance and concrete examples. Well front-loaded with the essential purpose.

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?

Tool has single parameter, read-only annotations, and existing output schema. Description adequately covers the discovery use case, return data characteristics (counts), and prerequisite relationship to searching. No gaps requiring additional explanation.

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?

Input schema has 100% description coverage and already lists common field examples (OverallStatus, Phase, etc.). The description repeats some examples in the context of the use case but does not add syntax details, format constraints, or semantic meaning beyond what the schema already provides. Baseline 3 appropriate 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?

States specific action ('Discover valid values') and resource ('ClinicalTrials.gov fields') plus key attribute ('study counts per value'). Clearly distinguishes from sibling tools like search_studies (which searches records) and get_field_definitions (which likely defines fields rather than listing their values).

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?

Explicitly states when to use ('explore available filter options before building a search'), establishing the workflow relationship to the search functionality. However, it does not explicitly name the sibling tool (clinicaltrials_search_studies) to use for the actual search phase.

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