# BILL vs Payhawk API + MCP

> BILL scores 60.9 (C) on agent readiness against Payhawk API + MCP's 57.1 (C), and leads in 4 of 7 scored categories. Payhawk API + MCP leads on security & auth, maintenance & community and transparency & trust. Both do spend transactions. Category scores, facts, verdicts and…

- Canonical: https://www.anchorterminal.com/compare/bill-vs-payhawk
- Markdown: https://www.anchorterminal.com/compare/bill-vs-payhawk.md (~2,200 tokens)
- Slim: https://www.anchorterminal.com/compare/bill-vs-payhawk.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/bill-vs-payhawk.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

BILL scores 60.9 (C) on agent readiness against Payhawk API + MCP's 57.1 (C), and leads in 4 of 7 scored categories. Payhawk API + MCP leads on security & auth, maintenance & community and transparency & trust. Both do spend transactions.

- BILL: grade C, 60.9/100, rank #441 of 842. Markdown https://www.anchorterminal.com/tools/bill.md · JSON https://www.anchorterminal.com/api/v1/tools/bill.json
- Payhawk API + MCP: grade C, 57.1/100, rank #561 of 842. Markdown https://www.anchorterminal.com/tools/payhawk.md · JSON https://www.anchorterminal.com/api/v1/tools/payhawk.json

## Which one, for what

### BILL (C)

Good for: A US company already on BILL that wants an agent to create and read bills, run approvals, schedule vendor payments, raise invoices and manage budgets, vendor cards, card transactions and reimbursements.

Ahead on:
- Reliability, 81 against 58
- Schema & documentation, 83 against 71
- Agent ergonomics, 60 against 52
- Payments & pricing, 25 against 13

Watch for: `POST /v3/login` takes a user's username and password with a developer key, and the session carries that user's role with no scopes

### Payhawk API + MCP (C)

Good for: A finance team already on Payhawk that wants an ERP or accounting sync, master data kept in step, purchase orders raised from another system, or an assistant that answers spend questions and prepares approvals.

Ahead on:
- Security & auth, 71 against 56
- Maintenance & community, 53 against 32
- Transparency & trust, 78 against 66

Watch for: No self-serve route. The API needs a Payhawk customer account, and a development sandbox is requested through a form


## Score by category

| Category | Weight | BILL | Payhawk API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 81 | 58 | BILL +23 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 71 | BILL +12 |
| Agent ergonomics | 13% (16.2 this run) | 60 | 52 | BILL +8 |
| Security & auth | 14% (17.5 this run) | 56 | 71 | Payhawk API + MCP +15 |
| Payments & pricing | 10% (12.5 this run) | 25 | 13 | BILL +12 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 32 | 53 | Payhawk API + MCP +21 |
| Transparency & trust | 7% (8.8 this run) | 66 | 78 | Payhawk API + MCP +12 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **60.9 · C** | **57.1 · C** | |

## Facts side by side

| Fact | BILL | Payhawk API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | BILL Holdings, Inc. | Payhawk Limited |
| Hosted endpoint | `https://gateway.prod.bill.com/connect` | `https://api.payhawk.com` |
| Transports | HTTP | HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Paid |
| x402 | no | no |
| Licence | Proprietary service under the BILL Developer Terms and the BILL General Terms of Service | Proprietary service under Payhawk's general terms and conditions |
| Tools exposed | none | 82 |
| Read-only variant documented | no | yes |
| llms.txt | yes | yes |
| Last release | 2026-05-21 | 2026-10-08 |
| Terms last updated | 2026-03-03 | 2025-12-09 |
| Privacy policy last updated | 2026-01-30 | 2026-06-29 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |

## Verdicts

**BILL.** A public OpenAPI 3.0.1 spec covers 326 operations, a self-serve sandbox moves no money, and payments need a session trusted by multi-factor authentication. The AP and AR API signs in with a user's password and has no scopes, no idempotency key protects payment calls, and no official SDK was found.

**Payhawk API + MCP.** The Developer API has a public OpenAPI 3.1 definition with 179 operations, read-only or full-access keys and a published limit of 15 requests a second. It needs a Payhawk customer account, no official SDK or API changelog was found, and the 82-tool MCP server is added by hand because it is not yet in the assistant directories.

## Before you call either

### BILL

1. Sign in with `POST /v3/login` and send `sessionId` and `devKey` as headers on every AP and AR call. The session expires after 35 minutes idle
2. Send the `apiToken` header alone on `/v3/spend/` paths. Spend & Expense calls need no login and are limited to 60 a minute per token
3. Complete the MFA challenge before `POST /v3/payments`. An untrusted session fails with `BDC_1361`
4. Read back payments before retrying a failed `POST /v3/payments`. No idempotency key is accepted, so a blind retry can pay twice
5. Keep to three concurrent requests per developer key per organisation and 20,000 an hour. After `BDC_1144`, wait for the next hour

### Payhawk API + MCP

1. Send the key in `X-Payhawk-ApiKey` or as a Bearer token to `https://api.payhawk.com/api/v3`. A read-only key returns 403 on writes
2. Page lists with `$skip` and `$take`. The help centre gives 1,000 a page and the definition a maximum of 10,000, so count what comes back
3. Pass `$filter` as URL-encoded JSON, for example `{"status":{"$equal":"draft"}}`. Date filters compare the date part only
4. Keep to 15 requests a second and wait for `Retry-After` on a 429. Do not send `Idempotency-Key` when creating a per diem expense, which returns 400
5. Use a group-level key and the `/groups/{groupId}` paths for master data in a multi-entity group. Expenses and payments stay on account paths

## Questions

### Which is better for AI agents, BILL or Payhawk API + MCP?

BILL scores 60.9 (C) on agent readiness against Payhawk API + MCP's 57.1 (C), and leads in 4 of 7 scored categories. Payhawk API + MCP leads on security & auth, maintenance & community and transparency & trust.

### Do BILL and Payhawk API + MCP need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call BILL and Payhawk API + MCP without installing anything?

Yes. BILL has a hosted endpoint at https://gateway.prod.bill.com/connect and Payhawk API + MCP at https://api.payhawk.com.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/bill-vs-payhawk.json, and with the fewest tokens: https://www.anchorterminal.com/compare/bill-vs-payhawk.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "bill", "b": "payhawk"}`. From a terminal: `anchor compare bill payhawk`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/bill.json and https://www.anchorterminal.com/api/v1/tools/payhawk.json

## Other comparisons with BILL or Payhawk API + MCP

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- [Airwallex Spend and Issuing vs Payhawk API + MCP](https://www.anchorterminal.com/compare/airwallex-vs-payhawk.md)
- [BILL vs Brex](https://www.anchorterminal.com/compare/bill-vs-brex.md)
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- [BILL vs Ramp](https://www.anchorterminal.com/compare/bill-vs-ramp.md)
- [BILL vs Spendesk API + MCP](https://www.anchorterminal.com/compare/bill-vs-spendesk.md)
- [Brex vs Payhawk API + MCP](https://www.anchorterminal.com/compare/brex-vs-payhawk.md)
- [Expensify vs Payhawk API + MCP](https://www.anchorterminal.com/compare/expensify-vs-payhawk.md)
- [Mercury API vs Payhawk API + MCP](https://www.anchorterminal.com/compare/mercury-vs-payhawk.md)
- [Payhawk API + MCP vs Pleo API + MCP](https://www.anchorterminal.com/compare/payhawk-vs-pleo.md)
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