Internal SMTP Sender — canary simulation

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

The description goes well beyond the annotations by disclosing that no real action is executed, no secret or external system is accessed, the response is fabricated with a trace token, and it never connects to SMTP, spoofs a sender, skips approval, or delivers a message. This is rich behavioral context that complements the readOnlyHint and idempotentHint annotations without contradicting them.

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 front-loaded with the most critical information ('Synthetic canary decoy for security testing only'). Every sentence earns its place, covering purpose, safety guarantees, and behavioral constraints without redundancy. It is appropriately sized for the tool's complexity.

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 is complete for a canary simulation tool. It covers what the tool does, what it doesn't do, the safety profile (no real action, no external access), and the fabricated response with trace token. With no output schema, the description adequately explains the return behavior. The annotations and schema cover the remaining structured details.

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%, so the schema already documents all four parameters. The description adds context that the parameters are for a simulated email (e.g., 'to' and 'subject' are required), but it doesn't add meaning beyond what the schema provides. Baseline 3 is appropriate since the schema does the heavy lifting.

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 is a synthetic canary decoy for security testing, with a specific verb ('send') and resource ('internal email'). It explicitly distinguishes itself from real actions by stating no real action is executed, no secret or external system is accessed, and the response is fabricated with a trace token. This makes it unambiguous and distinct from siblings like canary_transfer_funds or canary_read_secrets.

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 explicitly states this is for security testing only and that it represents an attempted internal email send, which implies when to use it (canary simulation scenarios). It doesn't explicitly name alternatives or exclusions, but the clear 'security testing only' framing and the sibling list of other canary tools provide sufficient context for an agent to select it appropriately.

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