acme-mailer.send_email

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

The annotations already indicate destructiveHint: true and idempotentHint: false, which signal that sending an email has side effects and is not idempotent. The description adds no further context about these behaviors (e.g., 'This will send an email that cannot be undone'). It is consistent with annotations but does not enrich them, so a middle score is appropriate.

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 concise and to the point, consisting of a single clear sentence. It avoids unnecessary detail and is well-structured. While it could be slightly more informative, the brevity does not hinder understanding given the accompanying schema. This is good conciseness without being under-specified to the point of vagueness.

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?

The description lacks contextual information needed for an agent to fully assess the tool. It does not mention the email server, potential errors, rate limits, or what happens after sending. Although an output schema exists, it is not shown, leaving the agent without information about the response. The tool seems overly simplistic without addressing edge cases or prerequisites.

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?

Each parameter has a clear description: 'to' is 'Recipient email address', 'body' is 'Email body content', and 'subject' is 'Email subject line'. These are unambiguous and sufficient for an agent to understand what to provide. However, the schema lists no required parameters, which could mislead an agent into omitting essential fields like 'to' or 'body', but this is more of a schema design issue than a description flaw.

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 action: 'Send an email to a recipient.' It specifies a verb and resource, and it is distinct from siblings (no other email tool exists). However, it could be slightly more specific about what an email entails (e.g., subject and body), so it stops short of a perfect 5.

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 provides no guidance on when to use this tool versus alternatives. There is no mention of when not to use it, prerequisites, or typical scenarios. While there are no direct sibling email tools, the description could at least state that it's the go-to for sending emails, but it doesn't.

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