list_accounts

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

The annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description goes well beyond them: it discloses that no mail server is contacted (local file read), that passwords and password sources are never returned, and the exact per-account field set. 'Never included' is a meaningful security guarantee an agent cannot infer from schema or annotations.

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 data source, then the return shape, then the two key caveats (no passwords, no network). Every sentence carries distinct information; nothing is repeated from the schema or annotations.

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 zero-argument, read-only discovery tool this is complete: the agent knows it needs no inputs, contacts no server, what each entry contains, and critically that the `name` field is the key to feed into all other tools. An output schema exists, so explaining return values further is unnecessary and the description does not overreach.

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?

Zero parameters, so the baseline is 4. The description correctly and explicitly confirms 'Takes no arguments', removing any ambiguity about whether an account filter is required, but there are no parameters whose semantics need further explanation.

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 (list accounts from accounts.toml) and enumerates exactly what each entry contains: name, email, provider, IMAP/SMTP hosts, auto-save flag. This clearly distinguishes it from the sibling set, which all operate on messages, folders, or attachments rather than accounts.

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?

Explicitly tells the agent that the returned `name` is 'the value to pass as `account` to every other tool', which effectively establishes this as the prerequisite discovery call. It also states it takes no arguments and does not contact any mail server, so the agent knows the cost profile. What's missing is an explicit 'call this first / before other tools' directive, though it is strongly implied.

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