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

Annotations only declare readOnlyHint=false/destructiveHint=false; the description adds real behavioral context: it returns SPF/DKIM deliverability hints that must be relayed to the user, requires addresses be copied verbatim as the user stated them, and specifies the required form action endpoint and per-field name attribute. No output schema exists, so this disclosure carries weight.

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 and scope, then prerequisites, then operational instructions. Every sentence contributes, though the implementation detail about the form action is a slight drift from the tool's own parameters.

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 comes back (deliverability hints) and states the precondition for the tool to matter. Nothing essential for correct invocation is missing, though permission or overwrite behavior for existing recipients is unstated.

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 all three parameters are already documented, and the description largely repeats the 1–5 recipient and subject-prefix facts. It adds only the handling instruction for recipients, which is marginal over 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+resource (set the contact form's notification recipients for a turbopress AI Launch website), including scope limits (1–5 addresses, optional subject prefix). An agent can distinguish this from siblings like set_email_forwarding or set_email_alias without opening the 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 a clear prerequisite — it is required before the website's forms work — which tells the agent when this must be invoked. It does not name alternatives or exclusion conditions, but the usage context is unambiguous.

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