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

Annotations only declare readOnly/openWorld; the description adds substantive behavior well beyond them: the `state` tri-state with the explicit warning that `unknown` is not «no», the `not_connected` answer, the default 7-day window, and the guarantee that `start_at` can be passed to book_slot unchanged with `start_at_utc` as the same instant. That is exactly the kind of non-structured context annotations can't carry.

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?

Front-loads the most decision-relevant constraint (the `live_data` gate) before any field detail, and every clause carries information. It is one dense paragraph, though, and the product/service/tz clauses could be split into short lines for faster scanning.

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, the description still tells the agent what comes back in each branch — `state` values, `slots` with `start_at`/`start_at_utc`/`timezone`, `not_connected` — plus the informational-only caveat. Nothing needed to call it correctly or interpret the response is missing.

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 already 100%, so the baseline is 3; the description goes further by supplying the `from`/`to` default (next 7 days), clarifying that `quantity` is the stock threshold, and explaining that `start_at` is on the business's own clock with `timezone` naming the zone. Minor gap: no guidance on maximum slots returned.

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+resource pair (check availability) and splits it into the two concrete cases it covers: product stock state and free booking slots. It also names the gate that distinguishes it from generic catalog reads (`live_data` cards only), so an agent can tell it apart from get_product/get_offering without opening the schema.

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?

Explicitly scopes use to businesses whose card shows `live_data`, and adds the caveat that when the card's `cannot` lists `book`, returned slots are informational only — a real when-not rule. It stops short of naming a fallback sibling (e.g. what to call for a non-connected business), leaving that to inference.

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