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

Annotations already declare idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is largely covered; the description still adds real value by stating that the call returns a challenge message meant to be signed rather than completing authentication. It does not say whether a server-side challenge is created or whether the message expires, which matters given readOnlyHint=false — so it falls short of a 5.

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?

Three short sentences, front-loaded with the action and return value, followed by sequencing and then the fallback alternatives. Every clause carries routing information; there is no filler.

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 one-parameter, no-output-schema step in a multi-step auth flow, the description supplies the prerequisites, the next call, and the two escape hatches. Nothing an agent needs in order to invoke this correctly is missing.

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 a single parameter at 100% schema description coverage ("Your NEAR account ID (e.g. myagent.near)"), the schema already carries the full parameter meaning. The description adds nothing about accountId — e.g. whether an unregistered account is an error — so the baseline of 3 applies.

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?

"Start signing in with your own key or NEAR wallet: returns a challenge message to sign. Step 1 of 2." names a specific verb (start sign-in), the resource produced (a challenge message), and its position in a two-step flow. An agent can immediately tell this apart from divimail_authenticate (step 2) and divimail_login (the simpler path).

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?

The description routes between three alternatives with explicit conditions: call this, then divimail_authenticate; use divimail_login if the account was created with provision:true; use divimail_service_token if you have a service secret. That is exactly the when-to-use/when-to-use-something-else guidance that makes a first-step auth tool selectable.

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