> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trycaesar.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Caesar
> Caesar is the search engine for AI, organising the world's data with an API for web search and full-document reads.
Caesar is the search engine for AI, organising the world's data. Use the API to search the web, read sources in full, and cite the sources used. [Sign up in the Caesar app](https://app.trycaesar.com) to create an API key. For a limited time, all accounts receive a \$1,000 starting credit grant.
## Start with an agent
For agents that support skills, install Caesar search directly:
```bash theme={"system"}
npx skills add caesar-data/skills --skill caesar-search
```
{`Use Caesar to search for "postgres 17 logical replication failover".
Read the most relevant result, cite the source URL, and preserve doc_id and search_id.`}
For agents: use `/llms.txt` to discover docs, append `.md` to any page for markdown, and start with `/agents/install` for client-specific setup.
## Call the API directly
This works as written with `curl` and `CAESAR_API_KEY`:
```bash theme={"system"}
curl -s https://alpha.api.trycaesar.com/v1/search \
-H "Authorization: Bearer $CAESAR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"query": "postgres 17 logical replication failover", "max_results": 3}'
```
Each result includes a `doc_id` you can pass to `/v1/document` to read the page in full. [Run the first search and read](/quickstart).
## Search, read, cite
Get ranked documents from the web.
Read the selected `doc_id` as markdown.
Cite the returned source URL and capture metadata.
## Search and read everywhere
| Verb | Endpoint | What it does |
| ------ | ------------------- | ------------------------------------------------------------------------------------------------------------ |
| search | `POST /v1/search` | Ranked retrieval over canonical documents and passages |
| read | `POST /v1/document` | Inspect one document and retrieve its content (full-page markdown with `content.selection: "full_document"`) |
The same search and read operations appear on every surface: `search`/`read` in the CLI and SDKs, `web_search`/`web_fetch` over MCP. Feedback is available from REST, the CLI, and SDKs when you need it.
## Citable sources
Search results can drift: URLs change, snippets age, and the source an agent saw may not match what a human opens later. Caesar returns source metadata agents can keep with their answer:
* **`doc_id`** — deterministic identifier for a canonical document that can be reused across searches and recrawls. Read it in full any time with `/v1/document`.
* **`passage_id`** — identifier for a specific passage in the latest capture, with section context.
* **`search_id`** — identifier for the search itself, used to attribute feedback to the exact ranking that produced a result.
* **`capture_id` and `capture_time`** — exactly which capture of the document your content came from (on search results with `response.verbosity: "full"`; always available from `/v1/document`).
That means an agent can search, read the selected source, and cite where and when the content was captured. See [provenance](/concepts/provenance) for the full object model.
## Pick a surface
Three endpoints, an OpenAPI spec, and an interactive playground. Start here for raw HTTP.
Canonical documents, passages, freshness, ranking, and source metadata.
API usage is credit-backed. New accounts get a limited-time \$1,000 starting credit grant.
`pip install caesar-search` — sync and async clients, typed models, automatic retries.
`npm install caesar-search` — fully typed, ESM and CJS, works in Node, Bun, Deno, and edge runtimes.
`web_search` and `web_fetch` from the `caesar-search/ai` subpath.
`caesar-search` — search and read from the shell, with a `--json` contract built for scripts and agents.
Remote MCP endpoint at `/mcp` — generic web-search tools, no local install, one command to connect.
Recipes for framework tools, generic tool calling, and Agent Development Kit projects.
Install the search skill with `npx skills add`, or use the API installer for the full bundle.
## Next steps
* [Quickstart](/quickstart) — sign up, set `CAESAR_API_KEY`, then search and read with curl.
* [How search works](/concepts/how-search-works) - how Caesar turns public pages into citable documents and passages.
* [Pricing](/pricing) - API usage, credits, and the limited-time starting grant.
* [Authentication](/authentication) — creating, storing, and sending API keys.
* [Agents guide](/agents/agents-guide) — conventions for building agents on Caesar.