Echo

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

Since no annotations are provided, the description carries the burden of behavioral disclosure. 'Echo a message back' conveys a side-effect-free operation and implies that the return value is the same message. The 'hello-world' comment adds useful context about the tool's simplicity, though it does not explicitly state the absence of side effects.

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 a single, front-loaded sentence that directly states the core behavior. The 'hello-world of MCP tools' phrase adds a small amount of contextual color without significant bloat, making the description concise and easy to parse.

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 single-parameter, trivial tool with no output schema, the description is sufficiently complete. It states what the tool does, the required parameter is fully documented in the schema, and the return behavior is clearly implied by 'echo back.' Nothing important is missing for an agent to invoke it 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 input schema already covers the only parameter, message, with a clear description and 100% coverage. The tool description adds no additional semantic detail about the parameter, such as formatting, examples, or constraints, so the baseline score of 3 is appropriate.

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 clearly states the tool's function: it echoes a message back. This is a specific verb and resource, and the purpose is immediately understandable. It does not explicitly distinguish itself from the sibling fetch_json, but the contrast is evident from the name and description.

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?

No guidance is given about when to use echo versus fetch_json or any other alternative. The 'hello-world' phrase hints at testing or demonstration use, but the description never states that this is for verifying connectivity or debugging, nor does it mention alternatives.

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