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

No annotations exist, so the description carries the burden and does add real behavioral context: results are relevance-ranked ('best answer first'), and omitting folder searches the whole box. It does not address result shape, cost, or whether matching is case/accent-insensitive, but the absence of anything alarming plus the explicit ranking disclosure is solid for a read-only search.

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 tight sentences that front-load the capability, then the prerequisite, then the usage heuristic. Minor redundancy: 'call list_sender_addresses to find the box' repeats what the box parameter description already says verbatim.

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?

No output schema and no annotations, yet the description covers scope, ranking, and where to get the required box value, which is enough to call it correctly. It stops short of describing what a returned thread looks like or how to page past the limit.

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 already documents q syntax, box format, limit range, and folder values. The description adds only a loose gloss of what q matches (subject, text, people, filenames), which is marginal value over the schema. 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 (finds threads of one mailbox) plus the searchable fields (subject, text, participants, attachment filenames) and the ranking behavior ('best answer first'). This is clearly a relevance search, distinguishable from enumeration siblings like list_conversations or retrieval via get_conversation.

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 both a prerequisite (call list_sender_addresses to obtain the box) and a clear use-case heuristic ('when you know a word of it and not where it is'). It does not explicitly name the alternative for the opposite case (enumerating a mailbox with list_conversations), so it stops short of full when/when-not coverage.

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