Send MIO Message

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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the mutation/irreversibility signal is covered structurally. The description adds the prerequisite lookup and the multi-recipient capability, but says nothing about whether the message is delivered immediately, whether a draft state exists, or how failures for some recipients in a batch are reported — useful context for a send operation.

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?

Three short sentences, purpose front-loaded, prerequisite second. The final sentence about multiple recipients is somewhat redundant with the recipient_id schema description, which keeps it from a 5.

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 4-parameter mutation with full schema coverage and no output schema, the description covers what to send and how to obtain the required ID. The main omission is outcome behavior — delivery timing and partial-failure handling for multi-recipient sends.

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% and each parameter is documented there, including the single-vs-array recipient form and the BCC-like hide_recipients flag. The description's mention of multiple recipients largely restates the schema, so it adds little beyond baseline.

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?

Specific verb+resource ('Send a new MIO message') that cleanly distinguishes it from sibling mutations like reply-mio-message, move-mio-message, and delete-mio-message. It does not explicitly name those siblings, but the word 'new' does the disambiguating work.

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 a concrete prerequisite workflow: look up recipient_id via search-people first. It stops short of stating when not to use it (e.g., use reply-mio-message to respond within an existing thread), so an agent must infer the exclusion from the sibling names.

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