generate_message

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

With no annotations, the description carries the behavioral burden. It discloses that the tool uses AI when credentials are present and otherwise falls back to producing a structured prompt, and it names the exact environment variables. This adds real behavioral context beyond the schema, though it stops short of describing error handling or the exact shape of the structured prompt.

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 sentences with no filler: the first names the action and output, the second covers the conditional AI behavior and fallback. Inessential details are omitted, and the key pipeline relationship is front-loaded.

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?

There is no output schema, so the description fills that gap by explaining the return value ('ready-to-use message') and how it feeds into send_postcard. It also documents the credential condition. The main missing piece is the structure of the fallback prompt, but the rich input schema and clear pipeline make the tool callable.

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 each parameter already has detailed descriptions, examples, defaults, and an enum. The description reinforces that recipient_context is the central input but adds little semantic value beyond the schema, so the baseline 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 states a specific verb and resource: 'Generate a personalized handwritten message for a postcard' based on 'context about the recipient.' It also ties the output directly to the sibling tool ('pass directly to send_postcard'), clearly distinguishing this generation step from the sending step.

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 makes the usage context clear: generate first, then pass the result to send_postcard. It also gives conditional guidance based on whether Cloudflare credentials are configured, though it does not explicitly list when not to use the tool or describe alternative approaches.

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