Design an Autonomous API Purchasing Workflow

The problem

Agents increasingly need paid capabilities mid-task: an enrichment lookup, a deep-research report, or an unplanned dataset. Without controls, “select a tool” quietly becomes “spend money”, and a timeout can turn into a duplicate charge. A good outcome is an agent that quotes before it buys, stays within an approved cap, executes once, verifies both the charge and the delivered result, and leaves an audit record without secrets.

Prompt

Give this to your agent once AIsa is connected via MCP:

Task: <what you need done>. Budget for the whole task: <your approved budget>. Ask me before any paid call; above <your threshold>, wait for my explicit yes.
Process for every paid step: (1) find the operation with AIsa `search`; (2) quote the exact call with `batch_quote`; (3) show me the operation, arguments, quoted cost, and remaining budget; (4) after I approve, run that same call once with `batch_use`.
If a quote is missing or failed, or the endpoint has no documented maximum, tell me and do not run it under the fixed budget. Re-quote if the operation or arguments change.
Never retry a paid call automatically after a timeout or unclear result: check usage first and report back.
At the end, give me an audit table: step | operation | quoted | approved cap | settled cost (or "unknown") | result verified?

APIs and Skills used

Through MCP, your agent reaches every operation via a few meta tools at https://mcp.aisa.one/mcp: search, list_categories, get_details, and batch_quote are free; batch_use (up to 20 calls) is billed per call.

Step	What the agent calls	Reference
Select	`search` / `list_categories` for the smallest sufficient operation	Connect via MCP
Estimate	`batch_quote` with the exact calls: returns the estimate without running anything	Quote, review, then execute
Authorize	Your policy layer and, above a threshold, a person	Security & Privacy
Execute	`batch_use` with the same calls, after approval	How It Works
Same over HTTP	`X-AISA-Cost-Mode: quote`, then `X-AISA-Max-Price-USD`	Billing & Credits
Verify payment	Balance, settled-cost metadata, Usage	Credit Balance, Usage
Handle rejections	`402` budget errors, `409` idempotency conflicts, retry rules	Error Codes
Pay per request without an account	MPP on selected read-only operations	Machine Payments

A quote, like X-AISA-Max-Price-USD over HTTP, checks the estimate before any provider is called; neither caps the final charge of a metered operation. The key’s spending limit in the Console is the hard ceiling. Machine payments (MPP). On operations that accept MPP, a request without credentials returns HTTP 402 with a WWW-Authenticate: Payment challenge; the agent pays through Tempo and retries with Authorization: Payment <credential>. The live challenge is authoritative for the amount and terms. Not every endpoint accepts MPP, so check the operation first.

Example output

Illustrative only. Operations and amounts are placeholders, not real prices or account records.

Step	Operation	Quoted	Approved cap	Settled cost	Result verified
1	`example_company_enrich`	`<quote A>`	`<cap A>`	`<settled A>`	Yes: record for Example Corp returned
2	`example_deep_report`	`<quote B>`	not approved (over threshold)	none	Skipped, asked user
3	`example_people_match`	`<quote C>`	`<cap C>`	unknown (timeout)	Not retried; flagged for reconciliation

Guardrails

Separate the stages: select, estimate, authorize, execute, verify payment, verify delivery, and audit. Selecting a tool never grants permission to spend, and a successful payment does not prove delivery.
Policy lives outside the prompt. Enforce allowed capabilities, per-call, per-task, and time-based limits, confirmation thresholds, and fallback rules in code or another trusted layer.
A quote is not approval, and a missing quote is not free. Re-quote when the operation, arguments, or scope change. Stop if the quote or documented maximum exceeds the remaining budget.
Execute once and keep identifiers. Preserve request, usage, and transaction IDs. Use idempotency keys only where an endpoint documents them (for example, synchronous Similarweb routes); never change a key to get past a 409.
Reconcile ambiguous outcomes:
- Rejected before acceptance: fix the request or pick another operation.
- No confirmed charge and no result: check status before any retry.
- Charge recorded, result missing: reconcile or contact support; do not repurchase.
- Result present, settlement unclear: keep the result and reconcile the charge separately.
- A network timeout does not prove the request failed before billing.
Audit without secrets. Record the task, decision, operation, approved and settled amounts, reference IDs, and outcome. Never store API keys, wallet secrets, payment credentials, or bearer tokens.
When a simpler flow is better: use normal account funding and application-controlled calls when usage is predictable, purchases do not need to happen at runtime, or you cannot reconcile ambiguous payment states.

Machine Payments

MPP for agents paying per request.

Billing & Credits

Quotes, caps, and settled cost.

Error Codes

Safe retry guidance.

Security & Privacy

Agent safety controls.

​The problem

​Prompt

​APIs and Skills used

​Example output

​Guardrails

​Related

Machine Payments

Billing & Credits

Error Codes

Security & Privacy

The problem

Prompt

APIs and Skills used

Example output

Guardrails

Related