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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds substantial context beyond them: it reads the domain's own .well-known and JWKS, refuses IPs/ports/local/private hostnames, and explains the canonical-domain identity rule (www vs apex, declared canonical_domain mismatch causes failure). These are exactly the behavioral traits an agent needs and cannot get from annotations.

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-loaded with purpose and scope before the usage rules, and nearly every sentence carries an operational constraint. The closing sentence restates the canonical-domain trust caveat already made earlier, which is mild redundancy rather than filler.

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?

For a one-parameter read-only verification tool with an output schema, everything an agent needs is present: what it reads, the failure conditions (private hosts, canonical mismatch), and the exact next call. Return values are covered by the output schema, so no gap remains.

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 100%, so the schema already documents the single 'domain' parameter and its pattern. The description adds genuine meaning beyond the schema: bare hostname only, public domains only, and the subtle canonical-identity semantics (www and apex are distinct, pass the canonical domain exactly). It stops short of 5 because the schema pattern already constrains the format.

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 and resource ('Verify that a vacation-rental host domain is a valid VRP node') and immediately scopes what it reads (.well-known/vacation-rental.json and JWKS). It clearly distinguishes itself from get_verified_stay_offer and hemmabo_search_properties, so an agent can route between them without opening 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?

Explicit when-to-use ('when a host domain arrives from outside search — user-typed or third-party'), an explicit alternative for the other case (domains from hemmabo_search_properties go straight to get_verified_stay_offer), and negative guidance (do NOT use to answer availability/pricing/booking/payment). It also names the follow-up call on success.

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