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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial context beyond them: required scopes ('email:read and access to that mailbox'), the exact returned fields, the untrusted-data warning, and the explicit note that it does not mark mail read. This is richer than the annotations require.

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?

The core action is front-loaded in the first sentence, followed by usage, prerequisites, and returns in a logical order. It is somewhat long and the return-field enumeration is dense, but each sentence carries information rather than filler.

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?

With no output schema, the description correctly takes on the burden of describing return values (sender, recipients, subject, text, content_status/recovery/retry, view_url, preferences with source/revision). Combined with auth requirements, side-effect disclosure, and the sibling alternative, an agent has everything needed to call it correctly.

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% and the schema itself already explains the message_id and the distinction from the provider Message-ID header. The description only restates 'given its InboxMCP message ID', adding no syntax or format detail beyond the schema, so the baseline of 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?

States a specific verb and resource ('Read one email's full text') scoped by an explicit identifier ('given its InboxMCP message ID'), and it also returns attached owner preferences. It contrasts itself with the get_email_context sibling, so an agent can distinguish it without opening the schema.

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?

Gives concrete when-to-use cases ('summarize an email, find a deadline or decide whether it needs a reply') and an explicit alternative plus condition ('use get_email_context instead when starting from an event ID'). It also rules out two adjacent behaviors ('does not mark source mail read or complete a batch'), leaving little to inference.

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