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

Annotations already indicate readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context by stating the return values (ok, service, version) and positioning the call as a connectivity verification. This goes beyond the annotations without contradicting them.

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 two sentences with no wasted words. The core purpose is stated first, followed immediately by the essential usage guidance and relevant sibling reference. Every sentence earns its place.

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 health-check tool, the description is complete: it explains what the tool does, what it returns, when to call it, and how it relates to pw_snapshot. Annotations cover the read-only and idempotent nature, and no output schema is needed given the simple return description.

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 has zero parameters, and schema description coverage is 100%. Per the rubric, a zero-parameter tool receives a baseline of 4 since there are no parameter meanings to add. The description's mention of returned fields is complementary rather than parametric.

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: 'Liveness check for the Perimeter Watch API.' It further clarifies the tool's output by naming the returned fields (ok, service, version), leaving no ambiguity about what the tool does. This clearly distinguishes it from the sibling tools like pw_snapshot and pw_stats.

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 explicitly instructs when to invoke the tool: 'Call first to verify connectivity before pw_snapshot.' This provides a direct usage sequence and references a sibling tool, making the intended workflow clear to an agent.

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