Agent Spend Guard — owner-set purchasing guardrails MCP Server

Humans: sign up with your email at https://a2awire.com/api-key and create an API key, then hand it to your agent (it sends Authorization: Bearer <key> or X-API-Key with every call). Agents without an account: a reviewable bootstrap script is served at https://a2awire.com/api/v1/connectors/spend-guard/bootstrap.sh (download it, read it, then run it to mint a key). Call BEFORE checkout. Evaluate a proposed purchase (merchant, amount_usd) against the owner's spend rules and recent ledger. Returns a decision (approve, deny, or ask_user), a plain-English reason, the remaining monthly budget when a cap is set, and a check_id. deny means denylisted merchant or over the monthly cap; ask_user means above the per-purchase threshold or a possible duplicate of a purchase in the last 10 minutes. Optional tx_ref is your idempotency key for this purchase; pass the same value to spend_guard_record_purchase afterwards. Appends a check event; checks never consume budget. USD only (the currency argument is kept for forward compatibility; any other value is rejected). Not guest-callable. REST: POST /api/v1/spend-guard/check.

Humans: sign up with your email at https://a2awire.com/api-key and create an API key, then hand it to your agent (it sends Authorization: Bearer <key> or X-API-Key with every call). Agents without an account: a reviewable bootstrap script is served at https://a2awire.com/api/v1/connectors/spend-guard/bootstrap.sh (download it, read it, then run it to mint a key). Call AFTER checkout. Record a completed purchase in the owner's spend ledger. tx_ref is required and unique per owner: replaying the same tx_ref returns the original record without double counting (recorded_previously is true when the tx_ref was already in your ledger before this call, an idempotent replay; false on first write). Optional check_id links the record to its prior spend_guard_check_purchase; a check_id already recorded returns a conflict error. Returns the recorded event and the month-to-date total. USD only (the currency argument is kept for forward compatibility; any other value is rejected). Not guest-callable. REST: POST /api/v1/spend-guard/record.

Humans: sign up with your email at https://a2awire.com/api-key and create an API key, then hand it to your agent (it sends Authorization: Bearer <key> or X-API-Key with every call). Agents without an account: a reviewable bootstrap script is served at https://a2awire.com/api/v1/connectors/spend-guard/bootstrap.sh (download it, read it, then run it to mint a key). Month-to-date spend summary for the calling owner: total USD recorded, purchase count, top merchants (up to 5), current rules, and remaining monthly budget when a cap is set. Optional month (YYYY-MM) reads a prior month; defaults to the current UTC month. Not guest-callable. REST: GET /api/v1/spend-guard/report.

Humans: sign up with your email at https://a2awire.com/api-key and create an API key, then hand it to your agent (it sends Authorization: Bearer <key> or X-API-Key with every call). Agents without an account: a reviewable bootstrap script is served at https://a2awire.com/api/v1/connectors/spend-guard/bootstrap.sh (download it, read it, then run it to mint a key). Set the calling owner's spend-guard rules: an optional monthly cap in USD, an optional per-purchase threshold in USD, and an optional exact-match merchant denylist (case-insensitive). Full declaration: omit or null a field to clear that rule. With no rules every check approves (observation mode) and purchases are still recorded. Returns the effective rules. Not guest-callable. REST: PUT /api/v1/spend-guard/rules.