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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds only the auth-scoping notion of an 'authorised project'; it says nothing about idempotency via operationId, what an ephemeral inbox with expiresIn does on expiry, or whether creation is reversible.

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 with zero padding, which is structurally sound. However its brevity comes at the cost of the missing detail noted elsewhere rather than through efficient packing.

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 six-parameter mutation with no output schema and low schema description coverage, the description should explain the ephemeral/persistent choice and expiry behaviour. It leaves the agent to guess at the most consequential parameters of a create operation.

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 33%: only projectId and operationId carry inline descriptions. The description mentions no parameters at all, leaving type (persistent vs ephemeral), prefix, expiresIn format and displayName semantics entirely undocumented outside the bare schema constraints.

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?

States a specific verb and resource ('Create a new inbox') with the scoping qualifier 'inside an authorised project', which is enough to separate it from read-side siblings like list_inboxes. It does not name any sibling explicitly, so it stops short of the top band.

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 guidance on when to use this versus list_inboxes or how it relates to other write tools; the only contextual hint is the implied 'authorised project' scoping. An agent must infer everything about preconditions and alternatives.

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