Intervals.icu MCP Server

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

With no annotations provided, the description carries full burden for behavioral disclosure. It describes what data is returned but doesn't mention authentication requirements beyond the optional api_key parameter, rate limits, error conditions, or whether this is a read-only operation. The description states it 'returns detailed metrics' which implies read-only behavior, but this isn't explicitly confirmed.

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 well-structured with a clear purpose statement followed by parameter documentation. Every sentence adds value, though the parameter documentation could be slightly more concise. The information is front-loaded with the core functionality stated first.

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 has an output schema (which handles return value documentation), 2 parameters with good semantic coverage in the description, and no annotations, the description is reasonably complete. It covers the purpose, what data is returned, and parameter semantics. The main gap is lack of explicit behavioral context like authentication requirements or rate limits.

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 providing clear semantic information for both parameters. It explains that activity_id is 'The Intervals.icu activity ID' and api_key is 'The Intervals.icu API key (optional, will use API_KEY from .env if not provided)', adding crucial context about the optional fallback behavior not evident from the schema alone.

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 with specific verb ('Get interval data') and resource ('for a specific activity from Intervals.icu'), distinguishing it from siblings like get_activity_details or get_activity_streams. It specifies what kind of data is returned (detailed metrics for each interval) and mentions grouped intervals as an additional feature.

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 implies usage context through the parameter documentation (activity_id is required, api_key is optional with fallback), but doesn't explicitly state when to use this tool versus alternatives like get_activity_details or get_activity_streams. No explicit guidance on when-not-to-use or comparison with sibling tools is provided.

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