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

Annotations provide readOnlyHint=false, idempotentHint=false, destructiveHint=false. The description adds genuine value beyond these: 'creating the link charges nothing', 'Stripe expires an unpaid link after 24 hours', 'an abandoned checkout charges nothing', and the guarantee that a published invitation's payment_status stays paid. These are non-obvious side effects an agent could not infer from the schema or 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 the core purpose, and every sentence is functional across the two operational modes and safety constraints. It is long, but the length is earned by genuine complexity; it could be tightened into structured bullets but contains no filler or redundancy.

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?

Given two operational modes, integration with three sibling tools, payment-side effects, and safety constraints, nothing an agent needs to call it correctly is missing. The output schema exists, so return values need not be explained, and post-payment verification steps are specified in detail.

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 already covers both params at 100%, so baseline is 3. The description adds value above that: how to derive quantity (pass publishing_price.credits_to_buy), the server-rejecting-changed-shortfall behavior, and the mode-dependent interpretation of event_id. This exceeds the schema, though it doesn't fully restate parameter formats.

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 ('start checkout', 'buy account credits') and the exact triggers (publishing, extra phone guests, design generations). It distinguishes itself from sibling tools by inlining the follow-up workflows (lemonvite_get_invitation, lemonvite_publish_invitation, lemonvite_get_account), so an agent can separate checkout from the other 14 tools 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?

Exceptionally explicit: states when to use (host buying credits), when NOT to call (before the host has seen and agreed to the amount), and fully splits the two modes (with event_id vs. omitted). It names the exact sibling calls to make after payment and the retry/authorization behavior, leaving no ambiguity about selection.

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