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

Annotations only flag readOnly=false, openWorld=true, idempotent=false, destructive=false; the description adds the material facts the agent actually needs: no card handling, a Stripe-hosted payment URL, a 1000-address/$349 floor, and the API-key requirement with where to obtain one. That is auth, output mechanism, and cost in one paragraph – well beyond the annotation bar.

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 what the tool does and what it returns, then price floor, then auth, then the when-to-call rule. Six short sentences, each carrying a distinct operational fact with no repetition of the schema.

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 12-parameter purchase tool with no output schema, the description supplies exactly what's missing structurally: the return value (Checkout URL), the payment handoff, cost floor, and auth prerequisite. An agent has enough to call it correctly and to explain the flow to the user.

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, but the description adds meaningful linkage: the minimum quantity ties to the 1000-address/$349 floor, and 'up to the count' implies checking availability via count_homes before buying. It doesn't touch the location parameters (zip/city/state/lat/lng) or recipientMode, which the schema carries alone.

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 deliverable: start buying a mailing list of matching homes, delivered as Excel plus CSV, returning a Stripe Checkout URL. It's unmistakably a purchase-initiation tool. It doesn't name the siblings (count_homes, preview_market) explicitly, but the word 'buying' and the checkout return make the distinction inferable.

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?

'Only call this when the user has clearly asked to buy' gives an explicit gating condition and implicitly separates it from counting/previewing. It also clarifies the agent's role in the payment flow ('the user opens it and pays there'). It falls short of a 5 because it never names the alternative tools an agent should reach for first.

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