voidmail_send_email

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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, idempotentHint=false): it names the policy error codes RECIPIENT_NOT_AUTHORIZED and CONTENT_CONTAINS_CREDENTIAL, guarantees nothing is sent in those cases, clarifies that success means provider acceptance rather than delivery, and warns against retrying uncertain sends. That is exactly the mutation-safety context an agent needs for an externally-visible write.

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?

Front-loaded correctly: the legacy/durability warning and the preferred alternative come first, before mechanics. Every sentence carries information, though the middle is a dense run of error-code and semantics clauses that could be split for readability.

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 must carry behavioral expectations itself, and it does: failure modes, the no-send guarantee, and the meaning of success are all covered. For an externally-visible send tool with only four annotation hints, nothing essential is missing.

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; that sets the baseline at 3. The description adds only the mild constraint that the recipient must be a single external address subject to recipient policy, with no additional format or body-selection syntax.

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 and resource ('Send email to one external recipient') and immediately distinguishes itself from the sibling voidmail_send_once by name. An agent knows this is the legacy, non-durable send path without opening either schema.

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?

Names the preferred alternative explicitly ('Prefer voidmail_send_once') and adds operational guidance ('Never automatically retry an uncertain send'). It stops short of stating the positive condition under which the legacy tool should still be chosen, so the routing is one-sided rather than complete.

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