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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing the concrete call limit (up to 15 mailboxes), the traversal order (address order), what happens when that limit is exceeded (response names skipped mailboxes), and how to continue (nextOffset). These operational constraints are not derivable from the schema or 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?

Three compact sentences, each load-bearing: scope first, constraint second, pagination mechanics third. No filler or restated title text.

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?

With no output schema and eight loosely constrained filters, the description supplies what the structured fields cannot: the result tagging ('tagged by mailbox'), the per-call mailbox cap, the skipped-mailbox reporting, and the continuation token. An agent has everything needed to call and paginate 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%, so baseline is 3, and the description adds real value on top: it establishes the cross-parameter constraint that at least one filter is required (required parameters is 0 in the schema, so this is otherwise invisible) and explains that offset be consumed as nextOffset from the prior response.

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 with explicit scope: 'Run one search across every reachable mailbox (optionally limited to one domain)'. It also names the sibling search_messages and clarifies the distinction ('same filters', different scope), so an agent can route between them 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?

Gives clear operating context: at least one filter is required, the domain parameter narrows scope, and offset should be fed from nextOffset. It implies when to prefer this over search_messages via the 'every reachable mailbox' framing, but never states an explicit exclusion or a direct 'use X instead when Y' rule.

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