Get an email

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is fully covered. The description adds a real behavioral detail: the shape of the failure result ({"error": "resource not found"}) for an unknown id. Beyond that, most of the text enumerates returned fields, which duplicates what the declared output schema already provides — little marginal behavioral context for a single-row read.

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?

Front-loaded with the verb and resource in the first line, then workflow, then return contract — a sensible order with no filler sentences. The verdict enumeration (spam/virus/spf/dkim/dmarc) is slightly listy but is concrete enough to earn 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?

With rich annotations and an output schema present, the description only needs to cover usage and edge cases, and it does: workflow anchor, error result for bad ids, and what makes this endpoint richer than a list row. The remaining gap is sibling disambiguation against get_email_raw and the id format, both minor given the structured fields.

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?

There is one required parameter at 0% schema description coverage, so the description must carry the load. It says the record is fetched "by id" and that an unknown id produces a not-found error, which is useful. But it never specifies the id's form or origin (e.g., whether it is the email id from list_emails rather than a message_id header, which the description itself mentions), leaving ambiguity an agent could hit at call time.

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 — fetch the full record of one email by id — and names the fields that distinguish it from a list view (body_text/body_html, inbound headers, spam/virus/SPF verdicts). It routes away from list_emails, but never distinguishes itself from the close sibling get_email_raw, which an agent could easily confuse with it.

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?

"Use this after list_emails to read a received reply's body" gives an explicit trigger and workflow position. It stops short of naming when-not-to-use or pointing at get_email_raw as the alternative for raw source, so the sibling boundary is left to inference.

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