> For the complete documentation index, see [llms.txt](/llms.txt).
> Markdown is also available via `Accept: text/markdown`. Full corpus: [llms-full.txt](/llms-full.txt).

# API Reference — The Signal API

Programmatic access to Return on Security's cybersecurity market dataset — funding rounds, acquisitions, companies, investors, and analytics.

Interactive HTML reference (Scalar): [/reference/](/reference/).
Machine-readable OpenAPI 3.1 contract: [/openapi.json](/openapi.json).

Base URL: `https://signal.returnonsecurity.com`

Authenticate every request with `Authorization: Bearer ros_live_…`.
See [index.md](/index.md) for quickstart, plans, quotas, and errors.

## Endpoints

Generated from the public OpenAPI spec (same file served at `/openapi.json`).

- `GET /api/v2/acquisition-category-data` — Acquisition data broken down by category
- `GET /api/v2/acquisition-geo-data` — Acquisition data broken down by target-company country
- `GET /api/v2/buyer-type` — Acquisitions grouped by buyer type (PE, Strategic, etc.)
- `GET /api/v2/category-data` — Funding data broken down by category
- `GET /api/v2/charts` — Main charts data with funding and acquisition aggregations
- `GET /api/v2/companies` — List all tracked companies
- `GET /api/v2/companies/{name}` — Get detailed data for a specific company
- `GET /api/v2/company-type` — Acquisitions grouped by company type
- `GET /api/v2/entitlement` — The caller's current plan, API entitlement, and remaining quota. Poll this (at most once a minute) to detect an upgrade landing instead of retrying a data endpoint; it answers while entitlement is lapsed, which is exactly when it matters.
- `GET /api/v2/filter-options` — Available filter options for the UI
- `GET /api/v2/funding-stage-percentiles` — Funding amount percentile heatmap by stage
- `GET /api/v2/funding/history` — Historical funding data over time
- `GET /api/v2/funding/instrument-breakdown` — Public-market capital by instrument type (senior notes, convertible notes, ATM equity, warrant activity) over time
- `GET /api/v2/investors` — List all tracked investors
- `GET /api/v2/investors/{name}` — Get detailed data for a specific investor
- `GET /api/v2/ma/history` — Annual M&A history — deal counts and disclosed values per year (exit-type breakdown for Pro callers)
- `GET /api/v2/pricing` — Machine-readable pricing catalog — plans, prices, and call allowances. Public and never quota-gated; the `upgrade.pricing_url` every paywall/quota refusal points at.
- `GET /api/v2/ranges/breakdown` — Transaction range breakdown analysis
- `GET /api/v2/stages/distribution` — Funding stage distribution analysis
- `GET /api/v2/top-acquirers-by-volume` — Most active acquirers by deal count
- `GET /api/v2/top-acquisitions` — Largest acquisitions ranked by amount
- `GET /api/v2/top-funding-rounds` — Largest funding rounds ranked by amount
- `GET /api/v2/top-investors` — Most active investors by deal count

## Related

- Guides: [index.md](/index.md)
- OpenAPI: [openapi.json](/openapi.json)
- Product MCP (live): https://mcp.returnonsecurity.com/mcp
- MCP server card: https://signal.returnonsecurity.com/.well-known/mcp.json