Developer documentation

x402 API documentation & agent guides

Build with 230 live pay-per-use API resources, free OpenAPI and MCP discovery, and x402 V1 + V2 exact payments on Base USDC. Separate product-commerce guides cover 27 digital products, 9 bundles, and SignalHarness Vault.

Documentation hub

Where to read next

Search by page, purpose, category, or status. API execution, downloadable-product commerce, and legal policy remain distinct. These public references are free to read.

45 documentation links
What the status badges mean
LIVE
An operating service, feed, or commerce channel.
CURRENT
The current published reference or policy; legal review is stated separately.
AVAILABLE
A product, bundle, or reference is available to inspect or obtain.
DRAFT
Draft text; not an effective policy.
PLANNED
A proposed capability that is not available.
PENDING
A specific prerequisite or publication step remains incomplete.
DEPRECATED
An older reference superseded by a named replacement.

Get Started

Discover capabilities, understand payment requirements, and make a first unpaid request.

Free discovery, a schema-valid unpaid request, and an authorized paid-client walkthrough.

Current published guidance.

Explore API-service and digital-product feeds in separate groups.

Public discovery is free; spending authority is separate.

Search live resource descriptions, exact per-call prices, schemas, and examples.

Public discovery is free; spending authority is separate.

How x402 V1 or V2 exact Base USDC payment authorizes service execution.

Current published guidance.

Configure HTTPS POST tool discovery and a payment-capable client.

Current published guidance.

Canonical schemas and paid POST routes for 230 API resources.

Public discovery is free; spending authority is separate.

Build with SignalHarness

Request lifecycle, schemas, errors, and recovery for application and agent developers.

Request, payment verification, finality, receipt, execution, and delivery.

Current published guidance.

Interpret 402, 4xx, pending, conflict, and uncertain outcomes; retry the same authorized payment.

Current published guidance.

Canonical request limits and response schemas for each enabled service.

Public discovery is free; spending authority is separate.

Open any service page for schema-valid examples and evidence limitations.

Current published guidance.

Choose compact machine-readable feeds and preserve purchase authority.

Current published guidance.

Guided product-use patterns; these recipes do not activate backend workflows.

Current published guidance.

Resolve product setup, discovery, payment-response, and recovery questions.

Current published guidance.

Inspect sample scope and source locations before selecting a digital product.

Sample content exists in the product source kits. Public sample download links have not been published; the samples page currently lists source locations only.

Product Commerce

Downloadable systems and Vault access have separate purchase paths from per-call APIs.

Compare downloadable systems and their Lite, Standard, and Premium contents.

Polar checkout and product Agent Pay are separate from API-service calls.

9 BundlesAVAILABLE

Inspect canonical bundle contents and existing bundle prices.

Downloadable product bundles.

Compare one-time digital-product prices and resource-specific per-call API prices.

Current published guidance.

One product-access plan with monthly or annual Polar recurring billing.

Active Polar commerce; no subscriber count is implied.

Compare Polar recurring subscriptions with separate x402 prepaid renewable terms.

Polar recurring access is active. Each x402 renewal requires a new payment; no automatic wallet debit. Product and Vault x402 execution is unavailable while its separate payment origin is owner-suspended. Public payment metadata remains available; the Netlify API services and Polar checkout are unaffected.

Review the 27-product catalog included under the canonical Vault plan.

Private downloads require a valid entitlement.

Understand the operating human checkout route and offering-specific purchase controls.

Current checkout guidance, not a payment receipt.

Free payment metadata for 90 one-time product offerings and 2 Vault terms.

Product and Vault x402 execution is unavailable while its separate payment origin is owner-suspended. Public payment metadata remains available; the Netlify API services and Polar checkout are unaffected.

Choose a product or bundle based on fit, scope, limitations, and licensing.

Current published guidance.

Agent Discovery

Free machine-readable routes. API-service and product catalogs have distinct authorities.

Static index of enabled API resources, prices, inputs, and examples.

Public discovery is free; spending authority is separate.

Read the current runtime API-resource catalog without payment.

Public discovery is free; spending authority is separate.

Machine-readable API operations and schemas.

Public discovery is free; spending authority is separate.

Connect to the JSON-RPC endpoint using the documented POST initialization and tools/list calls.

Public discovery is free; spending authority is separate.

Public metadata for enabled services; local metadata does not prove external indexing.

Public discovery is free; spending authority is separate.

Top-level catalog, discovery, and commerce routing information.

Public discovery is free; spending authority is separate.

llms.txtCURRENT

Compact routing instructions for agents entering the storefront.

Current published guidance.

Resource URLs and payment discovery metadata from the canonical registry.

Public discovery is free; spending authority is separate.

Inspect the existing SignalHarness listing on x402scan.

External directory; no endorsement or payment activity is implied.

Trust & Safety

Safety rules, agent buying policy, compatibility, and clear support boundaries.

TrustCURRENT

Discovery, authority, verified payment, and proof-of-delivery boundaries.

Current published guidance.

Non-destructive setup, permission boundaries, and protected data handling.

Current published guidance.

Machine-readable rules for purchase authority and safe buying behavior.

Current published guidance.

Review documented tool compatibility, conflicts, and installation assumptions.

Current published guidance.

Catalog practices and limitations; this is not a certification of legal compliance.

Current published guidance.

How agents discover, evaluate, and distinguish API execution from product purchases.

Current published guidance.

Product packaging, documentation, safe use, and licensing expectations.

Current published guidance.

Navigate delivery correction, refund review, and the support process.

Current published guidance.

Get support scope and contact the published support mailbox.

support@signalharness.ai

Legal

Published legal policies with source-recorded effective dates and review status.

Read the current terms of service and its stated scope.

Effective 2026-07-30; version 1.0.0-fl01. Owner-adopted; not attorney-reviewed.

Read the current privacy policy and its stated scope.

Effective 2026-09-02; version 1.1.0-sh01. Owner-adopted; not attorney-reviewed.

Rights and restrictions for digital-product and Vault downloads.

Effective 2026-07-30; version 1.0.0-fl01. Owner-adopted; not attorney-reviewed.

Read the current refund policy and its stated scope.

Effective 2026-07-30; version 1.0.0-fl01. Owner-adopted; not attorney-reviewed.

A first API request, without payment

Discover a service for free and POST its valid input. HTTP 402 returns payment requirements; it does not prove payment occurred. Before any paid retry, an authorized client checks the exact amount, Base network, USDC asset, recipient, resource, and expiry.

Unpaid request example

curl -i -X POST https://signalharness.ai/api/agent/services/json_schema_validate/invoke \
  -H "Content-Type: application/json" \
  --data '{"value":{"example":true},"schema":{"type":"object"}}'

Expected payment-required response

HTTP/1.1 402 Payment Required
PAYMENT-REQUIRED: <base64-encoded x402 V2 requirements>
Content-Type: application/json

{"x402Version":1,"accepts":["equivalent legacy Base requirement"]}

V2 clients decode PAYMENT-REQUIRED. V1 clients use the JSON body.
Both must validate amount, network, asset, payTo, timeout, and resource URL.

After prior spending authority, the client creates a payment signature and retries the identical request. Successful payment verification and finality precede execution. For 4xx input or payment errors, correct the reported issue before authorizing a new payment. For pending or uncertain outcomes, preserve the same request and payment identity.

Standing policies

The policies, summarized

License

Products and Vault downloads use a Single-Operator license: one operator plus the AI agents acting for that license holder. Broader Team, Agency, or Enterprise licenses are not currently offered. Licenses never transfer resale, redistribution, sublicense, or public-sharing rights to the raw kit files. Customer-created outputs remain theirs.

Refunds

14-day refund review if a product does not match its description. Missing, corrupted, or wrong-file delivery is corrected or reviewed for refund promptly. Duplicate purchases retain one entitlement and may be reviewed for a duplicate refund. Polar Vault renewals follow the published provider process; every x402 Vault renewal requires a new prepaid payment and never uses automatic wallet debit. Direct-wallet crypto outside x402 is inactive.

Onboarding

Product kits include quick starts, implementation docs, separate agent and human operating instructions, and integration guidance. The samples page currently lists sample scope and source locations; public sample download links remain pending.

Safety & install rules

Binding across every product: install into a clearly named new folder, never overwrite existing files, preview before applying, gate risky actions behind human approval, and ship a complete rollback path. These are catalog-level rules — see safety.

Support

Support scope and response targets are on the support page. The mailbox is live: support@signalharness.ai (verified 2026-07-07).

Frequently asked

Frequently asked questions

What are these products?

Execution systems and upgrade packs for AI-assisted work: prompt harnesses, quality-control scorecards, agent safety gates, and complete business operating systems. Plain-text file kits (Markdown + JSON) that work with any AI assistant.

Will this break my existing setup?

No. Every product is non-destructive by default: it installs into one new, clearly named folder, never overwrites existing files, includes a preview-before-apply step, and ships with a rollback guide. Removing a product means deleting its folder.

Do I need coding skills?

No. Every product has a 10-15 minute manual quick-start path. Advanced integrations (MCP, automation platforms) are optional and documented separately.

Do these work with my AI tool?

The kits are plain text and tool-agnostic: Claude, ChatGPT, or any LLM assistant. Per-product compatibility matrices list tested integration patterns.

Will these make me money?

No product here promises income or results. They are systems designed to help you execute more consistently and delegate to AI more safely. Outcomes depend on your product, market, and execution.

Can my AI agent use the product on my behalf?

Yes -- each product includes AGENT-README and agent operating instructions. Your license covers agents acting for you. Risky actions remain gated behind your approval.