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

Annotations declare openWorldHint=true, idempotentHint=true, destructiveHint=false. The description adds critical context beyond these: it submits mail externally with no approval override, accepted means provider acceptance only (not final delivery), unknown may already have been delivered, and repeating the call does not retransmit. This is rich behavioral disclosure not present in annotations.

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 core purpose and then layered with critical caveats. Slightly dense with multiple clauses, but every sentence addresses a real risk (retransmission, delivery ambiguity). Well-structured for a high-stakes mutation tool.

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?

Covers permissions required, external side effects, no approval override, return shape (draft details, status, review_url), failure semantics (accepted/sending/unknown/failed), and the correct alternative for status checks. Complete for a single-param mutation tool with no output schema.

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 description already explains the draft_id must be owner-approved. The description reinforces this ('exact draft recently approved by the owner') but adds no new syntax or format details beyond the schema. 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 and resource ('Send ... email draft') with a hard constraint baked into the purpose: 'Send only an exact draft recently approved by the owner in the InboxMCP browser.' This immediately distinguishes it from siblings like prepare_email_draft and get_email_draft.

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 names get_email_draft as the alternative for status checking and states the condition for 'awaiting_confirmation' (returns without sending). It also warns against retransmission on non-accepted results and tells the agent to inspect the sent mailbox before proposing another send.

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