Read Gmail Message (read-only)

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

Annotations already declare readOnlyHint/destructiveHint=false, so safety is covered. The description adds real behavioral context beyond that: body is truncated, attachment metadata shape, share-token restriction, and cost/auth ('$0.10; API key required'). Missing only things like rate limits or truncation size.

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-loads the core action, then return shape, then the alternative-tool routing, then constraints. Dense but almost every clause earns its place; the parenthetical output list runs slightly long.

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?

Output schema exists so return values need no expansion, yet the description still summarizes them helpfully. Combined with annotations, cost/auth notes, and sibling routing, an agent has everything needed to call this 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% so the baseline is 3, but the description adds meaning: message_id comes 'from search_gmail' and account is an optional mailbox selector for multi-mailbox cases. The id/email aliases are handled by the schema itself.

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 Gmail message by id') plus the source of the id ('from search_gmail'). It explicitly differentiates from the sibling read_gmail_attachment, so an agent can route without opening schemas.

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?

Names the alternative 'read_gmail_attachment for text/csv/vcf contents', explains when 'account' matters ('when multiple mailboxes'), and states a hard exclusion ('Share tokens cannot call'). Conditions for use and non-use are explicit.

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