send_email

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

No annotations are provided, so the description carries the full behavioral burden, and it falls short. It does not mention rate limits, suppression-list interactions (despite a list_suppressions sibling), authentication/domain-verification requirements (that constraint only appears in the schema for 'from'), or failure behavior. Only the word 'transactional' hints at intended use.

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 tight sentences, action-first, with the core capability front-loaded and the parameter modes following. Every clause earns its place with zero redundancy.

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 9-parameter mutation tool with a nested 'variables' object, no annotations, and no output schema, the description is minimally adequate. It covers the primary send modes but omits reply_to, the variables format, and any response or error expectations that an agent would need in the absence of an 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 only 67% (html, text, reply_to are undocumented), so the description must compensate. It does so by clarifying the mutually exclusive content paths — raw content vs. template — which is the key parameter relationship an agent needs to choose correctly, though it leaves reply_to and the variables object shape unexplained.

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?

States a specific verb (Send) plus resource (transactional email) and provider (Groundmail), which is immediately distinguishable from the read-oriented email siblings like list_emails and get_email. An agent can tell at a glance this initiates a send rather than a query.

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?

Gives clear context for the two invocation modes ('subject + html/text, or a published template_id / template_alias with optional variables'). It does not state exclusions or when-not to use it, but there is no competing send tool among the siblings, so the routing need is minimal.

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