# Foundations Elements

> UI encyclopedia for agents. Kind lists are 0.01 USDC; specs are 0.02 USDC on Base via x402 v2.

Directories should list GET /mcp/elements/search (0.02 USDC). GET /mcp/search is a working alias. Agents can start at GET /mcp/start (free briefing) or GET /mcp/elements (free kinds table). Pay with a PAYMENT-SIGNATURE header (or X-PAYMENT) that matches accepts[] from the 402. A settled x402 call is a Pro grant: Pro slugs and Pro fields. Max slugs need a Max account. POST /mcp needs a Foundations account.

Network: eip155:8453 (Base). Asset: USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913. Facilitator: https://facilitator.xpay.sh

## Docs

- [API reference](https://foundations.tensegrity.works/docs): paid and free HTTP paths, payment, errors
- [OpenAPI](https://foundations.tensegrity.works/openapi.json): machine schema
- [Pricing](https://foundations.tensegrity.works/pricing): 0.01 / 0.02 USDC
- [Lookup terms](https://foundations.tensegrity.works/terms): what one paid call buys

## Paid (send PAYMENT-SIGNATURE or X-PAYMENT)

- GET /mcp/elements/search — 0.02 USDC — cross-kind search (directory front door). Query q, kind, complexity, atomicType, domain, context, group
- GET /mcp/search — 0.02 USDC — alias of /mcp/elements/search
- GET /mcp/elements/{kind} — 0.01 USDC — kind list (slugs, aliases, complexity, atomicType)
- GET /mcp/elements/{kind}/{slug} — 0.02 USDC — spec body
- GET /glossary/{slug} — 0.02 USDC — spec body

## Free

- GET /mcp/start — start briefing (kinds, example slugs, next hops)
- GET /mcp/elements — kinds table (kind, count, path)
- GET /docs
- GET /llms.txt
- GET /openapi.json
- GET /pricing
- GET /terms

## Optional

- [Waitlist](https://tensegrity.company/elements?utm_source=x402&utm_medium=api): request an account
- [Human API docs](https://tensegrity.company/docs)
- [Human terms](https://tensegrity.company/terms)
- [Privacy](https://tensegrity.company/privacy)
- [Billing and payments](https://tensegrity.company/terms#s7)