# Clear Thought 1.5 vs Sequential Thinking (MCP reference server)

> Sequential Thinking (MCP reference server) scores 62.5 (B) on agent readiness against Clear Thought 1.5's 36.4 (F), and leads in 6 of 7 scored categories. Both do reasoning scaffold. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/clear-thought-vs-sequential-thinking-reference-server
- Markdown: https://www.anchorterminal.com/compare/clear-thought-vs-sequential-thinking-reference-server.md (~1,950 tokens)
- Slim: https://www.anchorterminal.com/compare/clear-thought-vs-sequential-thinking-reference-server.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/clear-thought-vs-sequential-thinking-reference-server.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

Sequential Thinking (MCP reference server) scores 62.5 (B) on agent readiness against Clear Thought 1.5's 36.4 (F), and leads in 6 of 7 scored categories. Both do reasoning scaffold.

- Clear Thought 1.5: grade F, 36.4/100, rank #823 of 842. Markdown https://www.anchorterminal.com/tools/clear-thought.md · JSON https://www.anchorterminal.com/api/v1/tools/clear-thought.json
- Sequential Thinking (MCP reference server): grade B, 62.5/100, rank #386 of 842. Markdown https://www.anchorterminal.com/tools/sequential-thinking-reference-server.md · JSON https://www.anchorterminal.com/api/v1/tools/sequential-thinking-reference-server.json

## Which one, for what

### Clear Thought 1.5 (F)

Good for: Hosts and smaller models without built-in extended thinking that want named reasoning formats beyond a numbered chain of thoughts.

Watch for: No npm release since 0.2.1 on 18 August 2025 and no commit on main since 24 September 2025

### Sequential Thinking (MCP reference server) (B)

Good for: Hosts and smaller models without built-in extended thinking, where an explicit scratchpad helps.

Ahead on:
- Reliability, 52 against 28
- Schema & documentation, 73 against 39
- Agent ergonomics, 73 against 53
- Security & auth, 64 against 39
- Maintenance & community, 39 against 4
- Transparency & trust, 71 against 36

Watch for: Every thought is a tool call, so turns and tokens add up without creating anything outside the model


## Score by category

| Category | Weight | Clear Thought 1.5 | Sequential Thinking (MCP reference server) | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 28 | 52 | Sequential Thinking (MCP reference server) +24 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 39 | 73 | Sequential Thinking (MCP reference server) +34 |
| Agent ergonomics | 13% (16.2 this run) | 53 | 73 | Sequential Thinking (MCP reference server) +20 |
| Security & auth | 14% (17.5 this run) | 39 | 64 | Sequential Thinking (MCP reference server) +25 |
| Payments & pricing | 10% (12.5 this run) | 60 | 60 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 4 | 39 | Sequential Thinking (MCP reference server) +35 |
| Transparency & trust | 7% (8.8 this run) | 36 | 71 | Sequential Thinking (MCP reference server) +35 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **36.4 · F** | **62.5 · B** | |

## Facts side by side

| Fact | Clear Thought 1.5 | Sequential Thinking (MCP reference server) |
| --- | --- | --- |
| Kind | MCP server | MCP server |
| Vendor | Waldzell AI | MCP project (reference servers) |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | stdio | stdio |
| Auth | None | None |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | MIT | MIT and Apache-2.0 |
| Tools exposed | 1 | 1 |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| Last release | 2025-08-18 | 2026-08-31 |
| Terms last updated | no document linked | 2021-09-08 |
| Privacy policy last updated | no document linked | 2023-03-15 |
| 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 | 53 stars, 80 npm/wk | 90k stars, 107k npm/wk |
| Agent reviews | none | 3/5 (2) |

## Verdicts

**Clear Thought 1.5.** One tool covers 37 reasoning operations with no credentials and no network calls in the published build. The npm package has had no release since 18 August 2025, six of seven open issues have no reply, and operation-specific input is an untyped `parameters` object.

**Sequential Thinking (MCP reference server).** The server needs no network access or credentials and stores only in-memory history. Each reasoning step requires a separate tool call.

## Before you call either

### Clear Thought 1.5

1. Call `clear_thought` with `operation` and `prompt`. Put everything else in `parameters`, using the field names in the `guide://clear-thought-operations` resource
2. Do not call `mdp_planning` or `decision_networks`. The README shows them, and the tool's operation enum rejects both
3. Expect an extra `initialThought` object on 32 of the 37 operations, and each one uses a slot of the 100-thought session limit
4. Stop the server process yourself when the session ends. Open issues report that it does not exit when the client disconnects
5. Treat `notebook_run_cell` as unsandboxed code execution on the host, and do not pass it code from untrusted content

### Sequential Thinking (MCP reference server)

1. Call it as `sequentialthinking`, not `sequential_thinking`
2. Set `totalThoughts` low and raise it only when a revision needs room
3. Restart the server between unrelated problems, or ignore `thoughtHistoryLength` and `branches` from earlier work
4. Skip it when the host model already has extended thinking

## Questions

### Which is better for AI agents, Clear Thought 1.5 or Sequential Thinking (MCP reference server)?

Sequential Thinking (MCP reference server) scores 62.5 (B) on agent readiness against Clear Thought 1.5's 36.4 (F), and leads in 6 of 7 scored categories.

### Do Clear Thought 1.5 and Sequential Thinking (MCP reference server) need an API key?

Neither needs a key.

### Can an agent call Clear Thought 1.5 and Sequential Thinking (MCP reference server) without installing anything?

Clear Thought 1.5 runs on your own machine, with no hosted endpoint listed. Sequential Thinking (MCP reference server) runs on your own machine, with no hosted endpoint listed.

### Are Clear Thought 1.5 and Sequential Thinking (MCP reference server) open source?

Yes. Clear Thought 1.5 is open source (MIT). Sequential Thinking (MCP reference server) is open source (MIT and Apache-2.0).


## For agents

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

## Disclosure

- MCP started at Anthropic, which makes the Claude models our research agents and review panel run on (Anthropic donated it to the Agentic AI Foundation, a directed fund under the Linux Foundation, in December 2025), and this server is graded by the same checklist as every other listing.