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

Annotations only declare the mutation profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false). The description adds substantial context beyond them: no provider/API key is accepted, a new fromAddress triggers an email verification flow, and email continues from the Bridge default sender until the link is clicked. That verification behavior is exactly the kind of non-obvious trait the description should carry.

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 with the core action, then behavior, then routing hints. Five sentences is on the longer side, and the 'there is no provider, account or API key to configure' clause is slightly verbose, but every sentence carries actionable information.

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?

No output schema exists, and the description compensates by stating what is returned ('the stored sender settings') and how to read them later via get_app. Combined with the verification caveat and the integration-guide pointer, an agent has everything needed to call this mutation correctly.

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 the baseline is 3, but the description adds real value the schema omits: the schema declares required=[] yet the description states 'at least one' of the two sender arguments must be supplied, and it explains the verification semantics tied to fromAddress. It stops short of detailing format constraints already in the schema.

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 ('Set the sender of the transactional email Bridge sends for the app') and immediately scopes what the email covers (invitations, password resets, magic links, MFA codes). This is clearly distinguishable from setup_payments, setup_sso, and update_branding among the siblings.

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 explicit preconditions (at least one of fromAddress/fromName), routing guidance to get_app for reading settings back, and a next-step pointer to get_integration_guide with topic=integration before writing app code. It also clarifies what the tool is NOT for by ruling out provider/API-key configuration.

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