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

Annotations declare readOnlyHint=false, destructiveHint=false, openWorldHint=true, but the description carries the real payload: no slot held, no provider notification, no payment collected. That resolves the apparent conflict between a non-readOnly tool that nonetheless performs no booking. It stops short of stating auth or email-verification mechanics/expiry, keeping it at 4.

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 short sentences, front-loaded with the action and then the negative constraints; every clause is load-bearing. The opening sentence is a long compound construction, but nothing is wasted or repeated.

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 need not be described. Given a mutating-adjacent, nested-object tool with annotations, the description supplies the one thing an agent most needs — what this call does NOT commit to — and adds no dead weight.

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?

With schema description coverage at 50%, the schema documents serviceId, startIso and the lat/lng origin, while partySize and the origin container are undocumented. The description adds workflow meaning ('customer-approved service, time') but no syntax, formatting, or per-parameter meaning beyond what the schema already states, so it does not compensate for the uncovered half.

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 verb and artifact — 'prepare an email-verified confirmation link on WellFred' — and immediately clarifies the boundaries ('neither books nor holds a slot'). This separates it cleanly from the search/browse/detail siblings without needing their schemas.

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 names the precondition for calling ('After the customer approves the returned service, time and known price/currency') and an explicit alternative path for a service class ('Option-based services use their canonical website URL instead'). It also steers downstream behavior ('Never claim a confirmed booking from this tool'), leaving little to inference.

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