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

Beyond the annotations (readOnlyHint=false, idempotentHint=false), the description discloses a rate limit (

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 core action and its deferred-pour behavior are front-loaded in the first sentence, with the rate limit and HTTP alternatives following. The privacy caution at the end is a useful closing constraint, though the in-character phrasing adds some density that a shorter form could have avoided.

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?

There is no output schema, so the description carries return behavior itself and does so by explaining the round waits behind the bar and is poured on the recipient's next visit, plus the 10/day limit and the privacy warning. It leaves minor gaps such as failure handling or whether the recipient is notified, but nothing critical for invoking it 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 patron_id, beer, note, signed_as, for_key, and for_note are already documented in the schema, including the enum values and defaults. The description echoes a few of these (the signed name, 'a line from you') but adds no syntax or format detail beyond the structured fields, which matches the baseline 3.

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 states a specific action (buy a free pour), the recipient (the author of a wall note or key holder), and the mechanism (it waits behind the bar and is poured on their next visit). It also distinguishes itself from the paid/house variants, which route over HTTP, so an agent can tell it apart from siblings like order or toast.

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 clearly frames the free-round context and routes paid pours for someone else and rounds for the house to different endpoints (POST /cantina/round/paid, /cantina/round/house). It does not explicitly compare against siblings such as toast or order, so the agent must infer when this beats leaving a note, but the positive context is clear.

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