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

Annotations already declare readOnlyHint=true, idempotent, non-destructive, so the safety profile is covered. The description adds genuinely useful behavior the annotations cannot convey: it opens nothing itself, returns procedural steps, and requires a separate browser tool call to actually complete the work. The note about Timely publishing no API docs explains why this is a guide rather than an API wrapper.

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?

Three sentences, front-loaded with purpose, followed by return behavior and the two-step execution path. The trailing 'Timely's official API: Timely publishes no API docs' is awkwardly phrased and slightly redundant, but overall size is appropriate.

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 parameterless, no-output-schema guide tool, the description covers what is returned (step-by-step screens, buttons, fields), what it does not do (opens nothing), and how to finish the task. It could mention that a live Cloud Browser session is required, but the essential picture is complete.

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?

The tool takes zero parameters, so there is no parameter meaning to add; baseline for a parameterless tool applies. The description correctly implies no inputs are required, avoiding the temptation to hallucinate arguments.

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 a specific verb and resource (reschedule appointment in the user's Timely account) and immediately clarifies the non-obvious nature of the tool: it returns step-by-step instructions rather than performing the action. It doesn't explicitly contrast with the sibling timely_book_appointment, but book vs. reschedule is self-evident from the names.

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?

Gives clear operational context: call this first to get the Timely screens/buttons/fields, then execute with the cotlet_browser_* tools in the user's Timely Cloud Browser. It does not state when NOT to use it or name the booking alternative for new appointments, so it stops short of full exclusion guidance.

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