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

Beyond annotations, it discloses substantial behavior: credentials are encrypted and never shown again, the password route avoids the chat, account.credential_added signals connection, calling again replaces and queued issues send next round, test_to sends a real email, and the operation is free. This is exactly the extra context annotations alone cannot convey.

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?

It is front-loaded with the core purpose, but the prose is long and rambling, with parenthetical asides and a redundant trailing 'Free. Free.' that should be cleaned up. Several clauses could be tightened without losing meaning.

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 an 8-parameter mutation tool with no output schema, the description covers the key flow (credential capture, link fallback, replacement, queue behavior) well. It leaves return-shape details implicit (relying on the named account.credential_added event), which is a small gap.

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?

With 100% schema coverage the baseline is 3; the description still adds value by explaining why password can be omitted (returns an owner link) and what test_to actually does (sends a verification email from that address). The remaining parameters are adequately covered by 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?

The description clearly states the verb (connect) and resource (the business's own SMTP email service) and gives concrete examples of providers. It does not explicitly name the sibling that disconnects or tests (newsletters_remove_service, newsletters_send_test), so sibling differentiation is only partial, but the core purpose is unambiguous.

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?

It gives clear operating context: call it with SMTP host, login and from address; omit password to receive an owner link; calling again replaces credentials; use from_a_terminal for the same from a terminal. It stops short of explicit 'when-not to use this vs. remove/test siblings', so it is not a full 5.

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