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

Annotations only establish safety (readOnly, idempotent, non-destructive, closed-world); the description adds the far more important behavioral fact that the call produces a procedural guide and performs no navigation or account action on its own, and that a browser session must follow. That is real value beyond the annotations. The trailing 'official API: Yes ... (checked 6 Nov 2026)' sentence muddies this by raising an API capability the tool apparently doesn't use.

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 core mechanism is front-loaded and the guide-then-browser handoff is stated compactly. However, the final sentence about Intervals.icu having a public REST API, complete with a 'checked 6 Nov 2026' date stamp, does not help the agent decide when or how to call this tool and reads as filler. The parenthetical '(screens, buttons, fields)' is useful; the API note is not.

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 zero-parameter, no-output-schema guidance tool, the description covers the two things an agent must know: what comes back (a step-by-step procedure) and what to do next (drive the browser tools). It does not describe how the guide should be relayed to the user or what happens if the browser flow fails, which leaves a small gap given the tool has no output schema to fall back on.

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?

There are zero parameters, so the baseline is 4 and the description is not required to explain argument meaning. It adds no parameter detail, but none is needed for an empty schema with additionalProperties false.

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 first sentence names a specific verb and resource (list calendar events in the user's own Intervals.icu account) and the second sentence immediately re-specifies what the tool actually returns: a step-by-step guide (screens, buttons, fields) rather than event data. That correction is essential but arrives late, so the headline claim still reads as if the tool performs the listing itself. The purpose is clear after a full read, but not from the opening clause alone.

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?

It states the usage path explicitly: this tool returns instructions and 'opens nothing by itself', and the actual action is then performed with the named cotlet_browser_* tools in the Intervals.icu Cloud Browser. That is unusually actionable routing guidance. It does not say when NOT to use it or whether sibling tools like intervals_icu_list_activities cover related data, so no exclusions are offered.

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