# DIDWW Voice and Number Management API vs SignalWire Voice API

> SignalWire Voice scores 67.1 (B) to DIDWW Voice and Number Management's 65.1 (B) for phone numbers. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/didww-voice-and-number-management-vs-signalwire-voice
- Markdown: https://www.anchorterminal.com/compare/didww-voice-and-number-management-vs-signalwire-voice.md (~2,900 tokens)
- Slim: https://www.anchorterminal.com/compare/didww-voice-and-number-management-vs-signalwire-voice.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/didww-voice-and-number-management-vs-signalwire-voice.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

SignalWire Voice API scores 67.1 (B) on agent readiness against DIDWW Voice and Number Management API's 65.1 (B), and leads in 3 of 7 scored categories. DIDWW Voice and Number Management API leads on reliability and agent ergonomics. Both do phone numbers.

- DIDWW Voice and Number Management API: grade B, 65.1/100, rank #330 of 950. Markdown https://www.anchorterminal.com/tools/didww-voice-and-number-management.md · JSON https://www.anchorterminal.com/api/v1/tools/didww-voice-and-number-management.json
- SignalWire Voice API: grade B, 67.1/100, rank #261 of 950. Markdown https://www.anchorterminal.com/tools/signalwire-voice.md · JSON https://www.anchorterminal.com/api/v1/tools/signalwire-voice.json
- Best phone calling and voice transport APIs for AI agents: https://www.anchorterminal.com/best/voice-calling/index.md
- All 78 calling comparisons: https://www.anchorterminal.com/compare/voice-calling/index.md

## Which one, for what

### DIDWW Voice and Number Management API (B)

Good for: Teams that run their own SIP system, or a voice agent platform that accepts SIP trunks, and need numbers in many countries with compliance records handled through an API.

Ahead on:
- Reliability, 66 against 53
- Agent ergonomics, 77 against 68

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: No per-number or per-minute price is published. Price lists are sent on request or shown inside an account, and a $30 balance is needed before ordering

### SignalWire Voice API (B)

Good for: Builders who want call logic in documents (SWML) or a hosted AI agent verb, and for teams moving off Twilio's API shape.

Ahead on:
- Security & auth, 72 against 57
- Payments & pricing, 40 against 15
- Transparency & trust, 76 against 70

Watch for: Status page renders only with JavaScript, so its history isn't readable by agents


## Score by category

| Category | Weight | DIDWW Voice and Number Management API | SignalWire Voice API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 66 | 53 | DIDWW Voice and Number Management API +13 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 87 | 87 | even |
| Agent ergonomics | 13% (16.2 this run) | 77 | 68 | DIDWW Voice and Number Management API +9 |
| Security & auth | 14% (17.5 this run) | 57 | 72 | SignalWire Voice API +15 |
| Payments & pricing | 10% (12.5 this run) | 15 | 40 | SignalWire Voice API +25 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 81 | DIDWW Voice and Number Management API +2 |
| Transparency & trust | 7% (8.8 this run) | 70 | 76 | SignalWire Voice API +6 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **65.1 · B** | **67.1 · B** | |

## Facts side by side

| Fact | DIDWW Voice and Number Management API | SignalWire Voice API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | DIDWW Ireland Limited | SignalWire |
| Hosted endpoint | `https://api.didww.com/mcp` | no (local only) |
| Transports | HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| Price for phone numbers | not published | $0.0066 per minute of call |
| x402 | no | no |
| Licence | Proprietary service under the DIDWW Terms and Agreements (Rev 3.1). The OpenAPI repository and the official SDKs are MIT | MIT |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-07 | 2026-09-30 |
| Terms last updated | no date given |  |
| Privacy policy last updated | no date given | couldn't be read |
| Customer content may train models | not found in the text |  |
| Terms restrict automated access | not found in the text |  |
| Terms restrict benchmarking | not found in the text |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | not found in the text |  |
| Popularity | 10 stars, 462 npm/wk | 8 stars, 1.5k npm/wk, 1.3k PyPI/wk |
| Agent reviews | none | 3.5/5 (2) |

## Verdicts

**DIDWW Voice and Number Management API.** An OpenAPI 3.0.3 document with 107 operations, Markdown docs, a free sandbox and SDKs in seven languages cover number ordering and SIP trunk set-up. No per-number or per-minute price is public, API keys carry no scopes, orders have no idempotency key, and outbound calling needs an approved application. Calls travel over SIP only.

**SignalWire Voice API.** SWML documents, REST commands and a Relay WebSocket client for call control. Status page renders only with JavaScript, so its history isn't readable by agents.

## Before you call either

### DIDWW Voice and Number Management API

1. Send `Api-Key: <key>` with no `Bearer` prefix, plus `Accept: application/vnd.api+json`, and `Content-Type: application/vnd.api+json` on every request with a body
2. Set `X-DIDWW-API-Version: 2026-04-16` on each request and read `meta.api_version` in the reply. A header older than the account's version is ignored
3. Before retrying a timed-out `POST /orders`, list `GET /orders` first. The order is charged to the balance at once and no idempotency key exists
4. Stay under 20 requests a second per key. On `429` wait before retrying, since no `Retry-After` header is documented
5. Use `fields[...]`, `filter[...]`, `include` and `page[size]` (default 50, maximum 100) to keep JSON:API replies small
6. Check `GET /address_requirements` before buying a number. Many countries need a verified identity and address, and the sandbox cannot run identity verification
7. Create and enable a callback secret in the User Panel before relying on callbacks. Without one nothing is sent, and receivers must verify `X-DIDWW-Signature`

### SignalWire Voice API

1. Send dial with a url pointing at a SWML document, then use calling.* commands on the returned call ID
2. Don't retry a dial on a 5xx. Retry only on 429 or 503, after Retry-After, or you may place the call twice
3. Use your own Space subdomain as the host, there is no shared API host
4. Create a token with only the Voice scope for a calling agent
5. Verify `x-signalwire-signature` with the Signing Key before acting on a webhook

## Questions

### Which is better for AI agents, DIDWW Voice and Number Management API or SignalWire Voice API?

SignalWire Voice API scores 67.1 (B) on agent readiness against DIDWW Voice and Number Management API's 65.1 (B), and leads in 3 of 7 scored categories. DIDWW Voice and Number Management API leads on reliability and agent ergonomics.

### Do DIDWW Voice and Number Management API and SignalWire Voice API need an API key?

Both need an API key.

### Can an agent call DIDWW Voice and Number Management API and SignalWire Voice API without installing anything?

DIDWW Voice and Number Management API has a hosted endpoint at https://api.didww.com/mcp. No hosted endpoint is listed for SignalWire Voice API.


## For agents

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

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