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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavior beyond that: `status` can lag after a credential is revoked, and connection viability must be read from connectionStatus/needsReconnect. Strong added context, though nothing is said about refresh timing or whether calling it triggers a sync.

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?

The return shape is front-loaded in the first sentence and the field list, while long, is load-bearing because there is no output schema. It is a dense run-on in places, but each sentence (return shape, top-level summary example, status-lag caveat) contributes something an agent needs.

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 carries full responsibility for describing returns, and it does so exhaustively down to individual fields plus example values for `summary` and `sayToHuman`. Combined with the sync-status caveat, an agent has everything needed to call this correctly and interpret the result.

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?

The schema has zero parameters, so there is nothing to document and the baseline is 4. The description correctly implies the tool takes no filtering arguments and always returns all registered inboxes.

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?

Opens with a specific verb+resource ('Returns { inboxes, sayToHuman }: every registered inbox') and enumerates exactly what each entry contains, so the agent knows it is a read-only enumeration of configured inboxes. It does not explicitly contrast with siblings like add_inbox or sync_inbox, but the listing scope makes the distinction inferable.

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?

There is no explicit when-to-use statement relative to alternatives such as sync_inbox, list_folders, or show_inbox; usage is implied by the listing semantics. However, it does give an actionable directive for consuming the results ('Check connectionStatus/needsReconnect, not status, to know whether an inbox can actually sync'), which is real guidance even if not tool-selection guidance.

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