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

Beyond the readOnly/idempotent annotations, the description discloses critical behaviors: unconfigured state raises a structured CONFIG_ERROR with no network attempt, unreachable returns `reachable: False` rather than erroring, it is never gated, and it never exposes `SIDECAR_AUTH_TOKEN`. This is rich, non-obvious behavioral context.

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 front-loaded with a one-sentence summary, then efficiently adds behavioral distinctions, error semantics, and security guarantees. Each sentence contributes distinct information, and the formatting with backticks and line breaks keeps it readable despite the detail.

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 read-only reachability probe, the description covers operational context, error behavior, result semantics, gating, and data safety. With an output schema present and annotations confirming read-only/idempotent behavior, nothing essential is missing for an agent to call this tool correctly.

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 only parameter `caller_id` is left entirely undocumented in the description, and schema description coverage is 0%. The description does not compensate for this gap or explain whether the parameter affects behavior. The impact is softened by the parameter being optional with a default, but the description still provides no semantic help.

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 opening sentence names a specific verb and resource: 'Live reachability probe against the deployed execution sidecar.' It further distinguishes the tool's server-side scope from a local `curl $SIDECAR_URL/health`, making its purpose unmistakable and distinct from the broader sibling health tools.

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 states when this tool is needed: it runs the probe from the SERVER's own network path, which a local curl cannot do. It also explains the meaningful distinction between 'not configured' and 'configured but unreachable', helping the agent interpret results and decide when this tool is the right check.

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