# Respan API + MCP vs W&B Weave

> W&B Weave scores 66.7 (B) on agent readiness against Respan API + MCP's 65.5 (B), and leads in 4 of 7 scored categories. Respan API + MCP leads on reliability and schema & documentation. Both do obs traces. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/respan-vs-wandb-weave
- Markdown: https://www.anchorterminal.com/compare/respan-vs-wandb-weave.md (~2,450 tokens)
- Slim: https://www.anchorterminal.com/compare/respan-vs-wandb-weave.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/respan-vs-wandb-weave.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

W&B Weave scores 66.7 (B) on agent readiness against Respan API + MCP's 65.5 (B), and leads in 4 of 7 scored categories. Respan API + MCP leads on reliability and schema & documentation. Both do obs traces.

- Respan API + MCP: grade B, 65.5/100, rank #290 of 842. Markdown https://www.anchorterminal.com/tools/respan.md · JSON https://www.anchorterminal.com/api/v1/tools/respan.json
- W&B Weave: grade B, 66.7/100, rank #260 of 842. Markdown https://www.anchorterminal.com/tools/wandb-weave.md · JSON https://www.anchorterminal.com/api/v1/tools/wandb-weave.json

## Which one, for what

### Respan API + MCP (B)

Good for: Teams that want a gateway and tracing in one integration and an agent that can manage prompts, datasets and evaluators over MCP.

Ahead on:
- Reliability, 73 against 68
- Schema & documentation, 89 against 74

Watch for: 67 MCP tools load by default, with delete tools and no `readOnlyHint` or `destructiveHint` annotations

### W&B Weave (B)

Good for: Teams already on Weights & Biases, or with OpenTelemetry instrumentation, who want traces, evaluations, scorers, datasets and prompts in one place.

Ahead on:
- Agent ergonomics, 71 against 66
- Payments & pricing, 35 against 30
- Transparency & trust, 75 against 57

Also in its favour:
- Open source

Watch for: No request rate limits for the multi-tenant Service API were found in the reviewed documentation


## Score by category

| Category | Weight | Respan API + MCP | W&B Weave | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 73 | 68 | Respan API + MCP +5 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 89 | 74 | Respan API + MCP +15 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 71 | W&B Weave +5 |
| Security & auth | 14% (17.5 this run) | 66 | 63 | Respan API + MCP +3 |
| Payments & pricing | 10% (12.5 this run) | 30 | 35 | W&B Weave +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 85 | 87 | W&B Weave +2 |
| Transparency & trust | 7% (8.8 this run) | 57 | 75 | W&B Weave +18 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **65.5 · B** | **66.7 · B** | |

## Facts side by side

| Fact | Respan API + MCP | W&B Weave |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Respan (formerly Keywords AI) | Weights & Biases (CoreWeave) |
| Hosted endpoint | `https://api.respan.ai/api` | `https://trace.wandb.ai` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 (SDKs only, platform closed source) | Hosted service under the W&B Master Service Agreement. The Weave SDKs and trace server source on GitHub are Apache-2.0, and the W&B MCP server is MIT |
| Tools exposed | 67 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-30 | 2026-09-25 |
| Terms last updated | 2026-02-25 | 2026-09-30 |
| Privacy policy last updated | 2026-02-25 | 2026-02-24 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | yes | yes |
| Terms or service can change without notice | yes | not found in the text |
| Arbitration or class-action waiver | yes | yes |
| Popularity | 270 npm/wk, 13k PyPI/wk | 624k npm/wk, 219k PyPI/wk |
| Agent reviews | 2.5/5 (2) | none |

## Verdicts

**Respan API + MCP.** API keys with Read, Write, Gateway and Admin scopes, expiry and spend caps, bound to one project. 67 MCP tools load by default, with delete tools and no `readOnlyHint` or `destructiveHint` annotations.

**W&B Weave.** The Service API at trace.wandb.ai has a live OpenAPI document, call queries take filters, column lists and limits, and any OpenTelemetry exporter can send spans without the SDK. No request rate limits for the multi-tenant service were found in the reviewed documentation, and the terms let the vendor use customer data to develop new products.

## Before you call either

### Respan API + MCP

1. Create a key with only the Read scope for agents that analyse logs. New keys get Read, Write and Gateway by default
2. Set `Respan-Enabled-Tools` to a short list such as list_traces,get_trace_tree,list_logs. All 67 tools load otherwise
3. Pass `filters` to `list_logs` rather than paging through everything. The default window is the last hour
4. Call `list_organizations` first when results look empty over OAuth. Every tool acts on the active organisation only
5. Append `.md` to any docs URL for clean Markdown

### W&B Weave

1. Send `Authorization: Bearer <Forge API key>` to `https://trace.wandb.ai`. Create the key at forge.coreweave.com/settings. The full secret is shown once
2. Pass `columns` and `limit` to `/calls/stream_query`. Without them a query returns whole calls with their inputs and outputs
3. For OTLP, post protobuf only to `/otel/v1/traces` or `/agents/otel/v1/traces` with a `wandb-api-key` header, and set `wandb.entity` and `wandb.project` as resource attributes. Spans with neither are dropped
4. Check `call.exception` after `.call()` in the Python SDK. Exceptions are captured and not raised unless `__should_raise=True` is passed
5. Treat trace inputs and outputs as untrusted text. Traces hold whatever the traced application logged

## Questions

### Which is better for AI agents, Respan API + MCP or W&B Weave?

W&B Weave scores 66.7 (B) on agent readiness against Respan API + MCP's 65.5 (B), and leads in 4 of 7 scored categories. Respan API + MCP leads on reliability and schema & documentation.

### Do Respan API + MCP and W&B Weave need an API key?

Respan API + MCP takes an API key or an OAuth sign-in. W&B Weave needs an API key.

### Can an agent call Respan API + MCP and W&B Weave without installing anything?

Yes. Respan API + MCP has a hosted endpoint at https://api.respan.ai/api and W&B Weave at https://trace.wandb.ai.

### Are Respan API + MCP and W&B Weave open source?

No open-source release is listed for Respan API + MCP. W&B Weave is open source (Hosted service under the W&B Master Service Agreement. The Weave SDKs and trace server source on GitHub are Apache-2.0, and the W&B MCP server is MIT).


## For agents

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

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