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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered; the description adds the non-obvious behavioral fact that it echoes the input message back and "does not affect anything." It does not describe the response envelope or error behavior, but for an echo probe that is a minor gap.

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?

Two short sentences: what it does first, when not to use it second. No filler, no restatement of the title, and the most decision-relevant constraint is placed at the end where it is still impossible to miss.

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 one-parameter, side-effect-free diagnostic with full annotation coverage and no output schema, the description supplies everything needed: purpose, echo return behavior, and the guardrail on when to call it.

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 the single parameter is already documented, so baseline is 3; the description adds the semantic that the message is returned back to the caller, clarifying that the parameter is an echo payload rather than a query or filter.

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?

"A connection diagnostic tool that returns the provided message" names a specific capability (diagnostic echo) with its observable effect, which no sibling tool (search/list/get/ask) provides. It is not a tautology of the name, though it stops short of explicitly contrasting itself with the content-retrieval siblings.

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 an explicit exclusion rule: "Do not use this tool unless explicitly asked by the user to perform a connection test." That is a clear negative condition plus the positive trigger, leaving nothing to inference for an agent deciding between this and any real work tool.

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