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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the session takes 'about 1 to 3 minutes,' is 'a relaxation exercise, not medical treatment,' and 'Nothing is saved' — the last point reinforcing non-persistence beyond what the 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?

Content is front-loaded: what it is, what happens, the session options, then when to use it. Every sentence carries information, though the session enumeration appears in both the description and the schema, creating some redundancy that a tighter version could avoid.

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?

With an output schema available and annotations covering safety, the description supplies everything else an agent needs: what the tool plays, how long it takes, the session choices, when to prefer it, and that nothing is persisted and it is not medical treatment. Nothing material for correct invocation is missing.

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?

Schema coverage is 100% and both parameters carry their own enum descriptions, including the session meanings, so the schema already does the heavy lifting. The description adds only marginal meaning — the 4-2-4-2 breathing pattern and the 'release breath' contextualize the breaths count — while largely restating the session list already present in the schema.

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 opens with a specific verb and resource ('Show Vayu's short guided pause in a timer') and then concretely enumerates the session content (three settling prompts, 4-2-4-2 breaths, a release breath) and the four named sessions. The clause 'a quick guided break or reset rather than a specific technique' distinguishes it from technique-oriented siblings without needing to name them.

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 gives an explicit when-to-use trigger: 'Use it when the user wants a quick guided break or reset rather than a specific technique,' which also implies the when-not case (a specific technique). It stops short of naming an alternative tool such as start_breathing_session, so routing still relies on the agent inferring which sibling is the 'specific technique' option.

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