list_subscriptions

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

Annotations provide readOnlyHint=true, but the description goes well beyond that, disclosing that opt-out options come from metadata fetches, that Gmail quota exhaustion can produce 'unknown', that dates bound the sample not the sender's history, and that there is deliberately no precomputed frequency. These are real behavioral traits an agent needs to interpret results correctly.

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 dense and front-loads the purpose, but it runs long with several sentences that could be tightened, and the flow moves between purpose, mechanics, field semantics, and usage guidance without clean visual separation. Every sentence earns its place informationally, but the size is above ideal conciseness.

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?

An output schema exists, so return values needn't be fully explained, and the description covers most of what's missing: field semantics for optOut, oldestDate/newestDate, newestThreadId, sendersFound, and sampling caveats. It's comprehensive for a 3-param list tool, though the query parameter's behavior could be explained slightly more.

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 0%, so the description must compensate, and it does substantially: it explains that max bounds the sample ('a query capped at max reaches back only as far as those threads go'), that topN truncation happens when sendersFound exceeds topN, and implies the query parameter's role through the 'mailbox slice' framing. The query parameter itself ('category:promotions' default) isn't explicitly discussed, leaving a minor gap.

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 clearly establishes the resource (sender-grouped mailbox slice with opt-out options) and distinguishes itself from siblings by naming triage_digest and list_unsubscribe as alternatives. The opening is slightly metaphorical ('Who keeps writing, how often, whether you can get off the list'), but it resolves into a precise function. It's clear what the tool does, though the verb is less direct than an ideal 5.

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?

Explicit 'USE WHEN' and 'DO NOT USE' sections name the exact scenarios and the sibling tools to prefer in each case: triage_digest for general inbox overview, list_unsubscribe for one known thread. This is textbook when/when-not guidance with alternatives.

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