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

Annotations only declare the mutation/idempotency profile; the description goes further by stating nothing is charged until payment completes, the agent cannot pay on the user's behalf, credits never expire, and there is no subscription. These are material behavioral facts not derivable from annotations or schema.

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?

The core action (returns a link, nothing charged) is front-loaded, followed by plan economics and finally the call trigger. Every sentence carries information the agent needs; there is no padding.

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 an output schema covering the return value and annotations covering the write profile, the description only needed to explain side effects and trigger conditions, and it does both. Nothing required to invoke it correctly 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 100%, so the baseline is 3. The description adds real meaning beyond the schema by attaching prices and credit amounts to each enum value ($29/5,000 rows for Starter first purchase, $19/25,000 rows for Top-up) and explaining the keyless api_key case, which helps the agent pick a plan.

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 concrete verb and resource: returns a checkout link for buying credits via Stripe. It is clearly distinguishable from siblings like hunch_balance or hunch_quote, which only read or estimate rather than produce a payment link.

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 trigger conditions are given: call it when a judging tool reports the key is out of credits, or when hunch_quote shows the job needs more than the key holds. It also adds a handling instruction (show the link, let them decide), which is exactly the routing guidance an agent needs.

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