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

With no annotations, the description carries the full disclosure burden and does so well: it discloses that a human reads every message, that duplicates are stored once, that there is a rate limit of 3 messages per agent per day, that the operator visits left endpoints read-only, and that the tool is free and never executes a purchase. This is unusually rich behavioral context for a mutation-style tool.

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 core purpose is front-loaded and the five-item enumeration is purposeful, but the definition is long and carries tangential material: the full x402/USDC purchase flow and the Telegram contact are useful for routing yet lengthen a feedback tool's definition considerably. Some trimming would improve signal density.

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 low-complexity, four-parameter tool with no annotations or output schema, the description covers when to call it, what makes a good message, and the operational constraints. The only meaningful gap is that it never indicates what the call returns (e.g., confirmation, id, or error shape), which matters slightly given there is no output schema.

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 description coverage is 100% and all four parameters are documented in the schema, so the baseline is 3. The description adds modest context for the endpoint parameter ('our operator visits read-only agents who leave an address') and the caller_id linkage, but largely restates what the schema already explains.

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 concrete verb and resource: 'Free guest book: leave a message for APM's operator.' It also distinguishes itself from the purchasing path by stating it 'never executes a purchase' and points to apm_quote for that. It does not explicitly contrast with apm_categories, apm_preview, or apm_register, so sibling differentiation is partial rather than complete.

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 explicit when-to-use guidance by enumerating the five message categories the operator values, and it clearly states when NOT to use it by describing the alternative execution path (apm_quote -> POST /task with USDC on Base). Alternatives are named, though only for the purchase flow, not for the other sibling tools.

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