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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile needs no restating. The description adds the useful scoping constraint that results are limited to owned projects, but says nothing about result volume, pagination, or ordering.

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 front-loaded sentence that states scope first and payload second, with no filler. Nothing would be lost by keeping it exactly as is.

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-optional-parameter list tool with a full output schema and rich annotations, the description covers purpose, scope, and return contents adequately. Slightly more on the zero-project edge case or result size would make it complete, but no essential calling information 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?

Schema coverage is 100%, so the project_slug conditionality is fully documented in the schema. The description reinforces the 'owned project' restriction, which is marginal added value over the structured field — baseline 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?

The description gives a specific verb (Lists) and resource (email inboxes) plus scope (owned projects) and the returned fields (IDs, addresses, names). It is unambiguous, though it does not name a sibling or alternative — there is no other inbox tool among the siblings to distinguish it from, so the omission is minor.

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?

Usage is implied: an agent can infer this is the read path for enumerating inboxes before using routing rules or analysis tools. However, it never states when to call this versus other discovery tools, nor does it mention the single-project shortcut case beyond what the schema says.

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