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

With no annotations, the description carries the full burden and delivers strong disclosures: the key is returned ONCE (a non-recoverable, effectively non-idempotent output) and the call is rate-limited to 5/hour per IP. It stops short of stating what happens on duplicate name/slug or whether the account is immediately active, so it is not fully transparent.

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 tight sentences, front-loaded with purpose, then the critical return-value caveat, then the rate limit. Zero waste; each clause carries actionable information.

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 2-param, no-output-schema tool, the description covers the one return value an agent must know (the one-time apiKey) and the operational limit. It lacks error/conflict behavior and any note on whether credentials are required, which is a minor but real gap given there are no annotations to fall back on.

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%, and the schema itself documents both name and slug constraints including the slug-to-mount-path mapping. The description adds no parameter meaning beyond that, so the baseline 3 applies.

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 ('Create a tenant account') and scopes it with the [x402 Paywall] prefix, clearly distinguishing it from the read-side sibling paywall_get_tenant. An agent can tell immediately this is the account-provisioning tool.

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?

Usage is implied by the purpose plus the follow-up instruction to store the key and set PAYWALL_API_KEY, which tells the agent what to do after calling. However, it names no alternatives or prerequisites (e.g. that this must precede authenticated paywall_* calls), leaving the when-to-use routing to inference.

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