imap_mark_as_unread

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

With no annotations, the description carries the burden of explaining behavior. It does disclose the single IMAP STORE round-trip behavior for arrays, which is useful. It does not mention connection requirements, error outcomes, or reversibility, but the core effect of marking emails unread is clear.

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?

Two sentences with no filler: the purpose is front-loaded, and the batching/IMAP STORE detail is directly useful for choosing how to pass UIDs. Every sentence earns its place.

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 simple mutation tool with a fully documented schema, the description is largely sufficient. It lacks any statement about the return value or prerequisites like an existing connection, and there is no output schema to fill that gap, so it is adequate but not fully complete.

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 full descriptions for all four parameters, including UID array semantics, atomicity, folder, and account resolution. The description repeats the single-vs-array distinction but adds little beyond what the schema already communicates, so the baseline of 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?

The description specifies a clear verb and resource: 'mark one or many emails as unread'. It also explains that it accepts a single UID or an array, and the operation is clearly distinct from siblings like imap_mark_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?

It provides useful batching guidance ('pass an array to flag N messages in one IMAP STORE round-trip'), so the agent knows when to use the array form. However, it does not explicitly compare this tool to imap_mark_as_read, imap_flag_email, or other alternatives, leaving tool selection mostly implied.

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