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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds the useful scoping note that results are limited to the authenticated user's accounts, but says nothing about pagination, ordering, or return shape beyond what annotations provide.

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?

A single sentence that front-loads the action and resource with zero filler. Every word earns its place and nothing is repeated from the title.

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-parameter, read-only listing tool with annotations and no output schema, the description is nearly sufficient: it establishes scope and implies no arguments. It could be complete with a note on pagination or ordering behavior, but that is a minor omission.

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 tool takes zero parameters, so the baseline is 4. The description correctly implies no input is needed by framing the listing as tied to the authenticated user, and there are no parameters whose semantics need clarifying.

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 states a clear verb ('List') and resource ('inbox accounts linked to the authenticated user'). It distinguishes from most siblings, which are mail-content operations rather than account enumeration. However, it doesn't explicitly call out the contrast with list_rules, the other list tool, so it falls just short of 5.

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 phrase 'linked to the authenticated user' implies the scope is the caller's own accounts and requires no arguments, which gives some context for when the tool applies. But it doesn't state when to use this rather than search_inbox or list_rules, nor does it mention any prerequisites or exclusions.

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