# Synth

> Synth Index searches reviewed, versioned research Contributions with exact citations. Access is through the `synth-ai` Python SDK, CLI, HTTP and hosted MCP.

## Start

- SDK: `pip install synth-ai==0.23.1` (wheel sha256 6f7d85b67888142bc45cab322c1cdbf2eeee1ba03ed6d60e30e79dc3cf4486e7)
- [Hosted MCP server](https://api.usesynth.ai/mcp)
- [Synth agent skill](https://docs.usesynth.ai/skills/synth/SKILL.md)
- [Python SDK (synth-ai on PyPI)](https://pypi.org/project/synth-ai/)
- [Get started](https://docs.usesynth.ai/sdk/overview)
- [Index quickstart](https://docs.usesynth.ai/synth-index/quickstart)
- [MCP reference](https://docs.usesynth.ai/reference/mcp)
- [SDK reference](https://docs.usesynth.ai/reference/sdk)
- [CLI reference](https://docs.usesynth.ai/reference/cli)
- [Index pricing and limits](https://docs.usesynth.ai/synth-index/private-search)
- [Docs index for agents (llms.txt)](https://docs.usesynth.ai/llms.txt)

## Site

- [Home](https://www.usesynth.ai/)
- [For agents](https://www.usesynth.ai/agents)
- [Docs](https://docs.usesynth.ai)

## Research

- [Scaling Train Time Compute for Gepa](https://www.usesynth.ai/research/scaling-train-time-compute-for-gepa): Scaling train-time compute for GEPA across public task containers — same-container comparisons, coverage curves, and proposer scaling evidence.

## Release notes

- [Synth v0.23: Index Search from the SDK and MCP, and weekly included usage](https://www.usesynth.ai/changelog/2026-10-16-synth-v023): Search cited research with FAST Search from the Python SDK, HTTP or hosted MCP, and start on a Free plan with $10 of usage every week.

## Synth v0.23: Index Search from the SDK and MCP, and weekly included usage

Source: https://www.usesynth.ai/changelog/2026-10-16-synth-v023

Synth v0.23 puts Index behind one typed Python SDK, one command line, and a hosted MCP server. Everything uses one
key. Install it with `pip install synth-ai==0.23.1`, sign up and start on the Free plan.

## Index Search from the SDK, HTTP and MCP

FAST Search returns a cited answer. Every citation points to the exact published revision it came from, and each result
reports output, accounting and cleanup state separately, so you know what you were charged and why.

- FAST Search is $0.05, drawn from your plan's included usage first.
- Searches are durable: create one, watch its events, read the result, and reattach from a new client.
- Index runs on `gpt-6-luna`, and Monitor reviews each result before it is delivered at no extra charge.
- Connect Claude Code with `claude mcp add --transport http synth https://api.usesynth.ai/mcp` and sign in.
- Browse published Contributions from the SDK or the hosted MCP server: `index.contributions.list` and `index.contributions.get` are available on both.

[Try the Index quickstart](https://docs.usesynth.ai/synth-index/quickstart)

## Weekly included usage on every plan

Included usage now resets every week, counted from the day your organization signed up.

| Plan | Price | Included usage |
| --- | --- | --- |
| Free | $0 | $10 per week |
| Standard | $20 per month | $60 per week |
| Max | $200 per month | $300 per week |

You can also buy credits in whole US dollars, from 5 to 10,000 per purchase. Credits are used last. The usage page keeps two numbers apart: what you consumed, and what was
charged and to which source (plan allowance, a promotion, credits, or not billed).

[See limits, usage and billing](https://docs.usesynth.ai/managed-research/usage)

## Fixes and improvements

- We improved sign-in: `synth-ai login` uses your browser, and `synth-ai login --with-token` stores an API key. Stored credentials are private files.
- We improved errors: failures arrive as typed exceptions with a code, status and request id, and limit refusals include `retry_after_seconds`.
- We fixed uncertain outcomes: if a call times out, resolve it with the saved mutation identity before you retry.
- We fixed Search waiting so a failed or cancelled Search raises right away instead of timing out.
- We improved capability discovery: ask the API which operations and limits apply to your organization before you call.

## Upgrading from 0.22

The Research facade and the standalone product modules are removed. Use `SYNTH_API_KEY` and `SYNTH_API_URL`; the older
variables still work but warn. Follow the [0.22 migration guide](https://docs.usesynth.ai/sdk/migration-v023).