Read one email (full body)

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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint. The description adds that HTML bodies are returned as-is (truncate client-side) and that marking as read is a separate action, reinforcing the read-only nature. No contradictions.

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?

Three concise sentences with no fluff. The first sentence immediately states the purpose, and subsequent sentences add necessary context and guidance.

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?

Given the complexity (4 parameters, read-only tool) and the presence of an output schema, the description is complete enough. It covers the main return types and how to use related tools. Minor omission: no explicit mention of auth prerequisites, but annotations include openWorldHint.

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 description coverage is 50% (only uid and include_html have descriptions). The description adds context about fetching headers, body, and attachment metadata but does not detail all parameters. Baseline 3 is appropriate as the description provides some additional meaning beyond the schema.

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 clearly states it fetches one email by UID with headers, body, and attachment metadata. It distinguishes itself from sibling tools like proton_get_attachment (for downloading attachment bytes) and proton_flag_email (for marking as read).

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?

Explicitly states when to use (to fetch full email) and provides alternatives: proton_get_attachment for downloading attachments and proton_flag_email for marking as read. Also advises on handling large HTML bodies.

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