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

With no annotations, the description carries the full burden. It usefully discloses token/project scoping and that the response echoes limit and offset, but says nothing about read-only semantics, ordering, what an inbox object contains, or how the taskStatus filter interacts with results.

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?

Two sentences, zero filler, and the identifying information is front-loaded ahead of the pagination detail. The telegraphic second sentence ("response echoes both") is efficient but slightly cryptic in isolation.

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 four-parameter read tool with no output schema and no annotations, the description should sketch what comes back. It names the resource and pagination echo but omits the shape/order of returned inboxes and ignores two of the four parameters entirely.

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 baseline is 3; the description earns above that by explaining that limit/offset are reflected back in the response, which the schema does not state. It still adds nothing about projectId's constraint or the taskStatus enum beyond what the schema already says.

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 opens with a specific verb and resource ("List the principal inboxes") and adds a precise scope ("visible to the API token, scoped to the token project"). It doesn't explicitly differentiate itself from siblings like list_messages or get_message, so it stops short of a 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?

Usage is only implied: an agent can infer this is the discovery step before calling list_messages, but the description never says so and names no alternative or exclusion. There is no explicit when-to-use or when-not-to-use guidance.

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