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

Annotations already establish the safety profile (idempotent, non-destructive, not read-only). The description adds non-obvious side effects beyond that: running follow-ups stop, and active campaigns pause when the bounce breaker stopped the mailbox. It stops short of auth requirements or return details, but the side-effect disclosure is genuinely useful.

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-loads the core action, then layers side-effect and return-value details. Four compact sentences, each carrying information, though the final alias_verified sentence is slightly abrupt out of context.

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?

With no output schema, the description usefully explains what alias_verified conveys, and it covers the mutation's cascading effects. Combined with the annotation safety profile, an agent has enough to invoke it correctly, though prerequisites and confirmation semantics for the 'confirm' guard are left implicit.

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 coverage is 100%, so all three parameters are documented in the schema itself. The description only reaffirms the connection_id source ('id from get_mailboxes') and mentions alias_verified without tying it to a parameter, adding marginal value over the schema. Baseline 3 is appropriate.

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 ('Make the project send from one of your connected mailboxes') with an explicit reference to the sibling that supplies the id (get_mailboxes). An agent can distinguish this from unlink_project_mailbox and set_from_alias without opening a 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?

Gives clear context for use (changing the sending mailbox) and routes the agent to get_mailboxes for the connection_id. It does not, however, explicitly contrast this with alternatives like set_from_alias or unlink_project_mailbox, so it falls short of full when/when-not guidance.

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