update_message

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

With no annotations provided, the description carries full responsibility for behavioral disclosure. It reveals atomic execution, the bulk-update helper, the IMAP ordering constraint, and even mentions a 'narrow-path optimization' with source_mailbox. It does not mention idempotency or error handling, but the atomicity and ordering are well covered.

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?

The description is compact and front-loaded: the main purpose is stated in the first sentence, then the patch semantics and order of operations follow in clear, short paragraphs. There is no filler; every sentence adds necessary context for correct invocation.

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 tool's complexity (8 parameters, atomic batch update, IMAP constraints, and replacement of three prior tools), the description covers all critical aspects: what it does, when to use it, how it behaves atomically, and the order of operations. An output schema exists, so return values are not the description's responsibility. No essential information for an agent to call the tool correctly is missing.

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?

The input schema already provides 100% coverage, describing each parameter and their interplay (e.g., 'flag_color implies flagged=True unless none'). The description adds patch semantics as a general principle, but does not enrich individual parameter meaning beyond the schema. The baseline of 3 is appropriate because the schema does the heavy lifting.

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 starts with a precise verb-resource pairing: 'Update one or more messages: change read state, flag, and/or move, in one atomic call.' It enumerates the exact operations and states it is atomic. It also explicitly distinguishes itself from prior separate tools by naming them and saying it replaces them.

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?

The description provides explicit when-to-use guidance: it lists the three legacy tools it replaces, so an agent knows to prefer this consolidated tool. It also explains patch semantics ('caller specifies only the fields to change') and gives operational order ('read-state and flag changes apply first, then the move'), which is essential for correct IMAP usage.

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