update_draft

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

Annotations already flag destructiveHint=true and openWorldHint=true, but the description adds material behavior beyond them: recipients and subject are preserved, the quoted original is retained unless keepQuote is false, the draft receives a NEW UID, and nothing is sent. The UID-change behavior in particular is non-obvious and operationally important.

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?

Four short sentences, front-loaded with the core action, followed by invariants, the UID consequence, the eligibility constraint, and the safety note. No sentence is redundant padding.

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?

For a mutation tool with no output schema, the description covers what is replaced, what is preserved, the side effect on the UID, the eligibility restriction, and the fact that nothing is sent. An agent has everything needed to invoke 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 description coverage is 100% and already documents uid, body, and keepQuote (including its default). The description largely restates these ('quoted original is kept below the new text unless keepQuote is false', 'new reply text'), adding little syntax or format detail beyond the schema, so the baseline 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 ('Replace the reply text of a draft') and scopes it to drafts 'created by this server', which cleanly distinguishes it from create_reply_draft and the read-only siblings. An agent can identify the operation 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 clear preconditions: only drafts created by mail-brief-mcp can be changed, and the caller must use the newly returned UID. It does not explicitly contrast with create_reply_draft or state when to prefer updating over recreating, so it falls short of full alternative routing.

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