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

Annotations already cover the safety profile (readOnly=false, destructive=false, idempotent=true), so the bar is lower; the description still adds real value by declaring the immutable field constraint ('address cannot be changed'). It does not mention permission requirements or whether the rename is reflected on previously sent mail, so it falls short of 5.

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 short sentences, zero filler, with the actionable scope stated first and the constraint second. Every clause earns its place.

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?

An output schema exists, so return values need no explanation, and the annotations plus schema cover the mutation semantics. The remaining gap is absence of usage/authorization context for a write operation, which keeps it just below complete.

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 67%, and the two optional parameters' descriptions already carry the omit-to-keep / null-clears semantics and length limits. The description only restates which fields are updatable ('internal name', 'outgoing sender name'), adding little beyond the schema, so the baseline 3 is appropriate.

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 (Change) and resource scope (an inbox's internal name or outgoing sender name), and adds the boundary that the address cannot be changed. No sibling performs inbox renaming, so an agent can route to this tool confidently.

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 by the mutation verb and the 'address cannot be changed' exclusion, but there is no explicit guidance on when to use this versus get_inbox, create_inbox or delete_inbox, and no prerequisites (e.g. permissions on the inbox) are stated.

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