wait_for_email

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

Annotations already declare readOnlyHint=true, idempotentHint=true, so the tool is safe and idempotent. The description adds key behavioral context: it blocks, can time out, and returns a specific structure on timeout ({timed_out:true}). It doesn't mention rate limits or resource consumption, but for a read-only blocking poller with annotations, this is strong.

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 two sentences long with no wasted words. It front-loads the core behavior ('Block until...'), then gives usage guidance, and finally notes the return value. 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?

Given the tool has no output schema, the description compensates by explaining the return format (full message or {timed_out:true}). It doesn't explicitly state all possible return fields, but for a waiting tool with good annotations and schema, it's nearly complete. A mention of the format of the returned message would push this to 5.

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%, with all 4 parameters clearly documented. The description mentions the return format but adds no additional parameter semantics beyond the schema. Baseline 3 is appropriate.

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 states the tool blocks until a matching email arrives or times out, using specific verbs ('Block', 'wait') and the resource ('email in a mailbox'). It distinguishes itself from siblings like list_inbox by explicitly saying it replaces polling.

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 explicitly tells when to use the tool: 'Call this when you just sent an email and need the reply, or are expecting an inbound message — instead of polling list_inbox yourself.' This provides clear context and mentions the alternative (list_inbox) to avoid.

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