send_email

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

Annotations are minimal (readOnlyHint=false, idempotentHint=false, no safety details), so the description carries the transparency burden. It adds valuable context: the requirement that from.email must match a verified account, the availability of list_domains for checking, and the return behavior (message ID and queue status). It doesn't disclose rate limits or error cases, but it goes well beyond the annotations.

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?

Exactly two sentences: the first states what the tool does, the second covers the critical prerequisite and return value. No filler or redundancy, with the key action 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?

This is a complex tool (12 params, nested objects, no output schema), but the schema is exceptionally rich with per-field limits and descriptions. The description adds the missing big-picture context: purpose, verification prerequisite, and return format. It lacks details on async queue behavior and error conditions, but the overall package is solid.

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 baseline is 3. The description adds minimal parameter-level meaning beyond the schema — the from.email verification constraint is already restated in the schema's 'from' property description. The description's mention of return values is useful but not parameter semantics.

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 uses a specific verb+resource combination: 'Send a transactional email from a verified MisarMail account.' The phrase 'transactional email' clearly distinguishes this from sibling tools like send_campaign, and the verification constraint adds scope specificity.

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 clear usage context by emphasizing 'transactional' versus campaign/marketing emails and explicitly references list_domains as a prerequisite to check available sender domains. However, it doesn't explicitly name alternatives (e.g., 'for campaign emails, use send_campaign instead'), so it earns a 4 rather than a 5.

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