[Feature Request]: optional feeless (Nano/XNO) settlement rail for metered search requests #585

Feature request: optional feeless settlement rail for Algolia metered search requests

Is your feature request related to a problem?
Algolia prices search/retrieval per 1,000 requests on the metered plans (Grow $0.50/1K searches after the free 10K/mo, Grow Plus $1.75/1K). An AI agent issuing many single retrieval calls to an Algolia index pays a fraction of a cent per call. On a card or EVM-L2 (USDC) settlement path the fixed per-transaction fee can exceed the value of an individual search, so per-call payment authority is uneconomical even though the metered unit is a per-request charge.

The idea
Add an optional, backward-compatible way to settle metered search requests feelessly (Nano / XNO) beside the existing account/card billing — for example a client-side opt-in that meters a request and settles it with a fee-free rail, defaulting to the current billing when unset.

Why Algolia specifically
Algolia already sells search per-request (per-1K metering), which is exactly the unit a settlement rail should attach to. A fee-free rail removes the fixed-fee overhead that makes sub-cent per-request settlement uneconomical, so autonomous agents can pay exactly for what they call.

Existing building blocks (reuse, not from scratch)

• x402 (HTTP-402 payment standard; x402-foundation/x402) with the exact scheme used for fee-free Nano settlement.
• x402nano (x402nano.org) — permissionless exact-permit2 Nano facilitator.
• feeless402 (github.com/michardnicolas/feeless402) — Python wallet, x402 client, merchant server, MCP server.
  The request is only a client surface to opt into one; the signing/facilitation/settlement legs already exist.

A working model of the economics (tested locally)

Grow:       $0.50/1K  -> $0.0005 / search
  10,000 searches: usage $5.00
  + L2-USDC gas (0.0015/tx): $20.00 (300% overhead)
  + feeless rail (Nano):     $5.00  (0%)
Grow Plus:  $1.75/1K -> $0.00175 / search
  10,000 searches: usage $17.50
  + L2-USDC gas (0.0015/tx): $32.50 (86% overhead)
  + feeless rail (Nano):     $17.50 (0%)

At split-cent per-request prices a fixed $0.0015/tx fee dominates; a feeless rail removes it.

Requested scope

• Whether per-request (per-1K) settlement on a fee-free rail is something Algolia would consider for agent workloads.
• If so, an opt-in client-level settlement='nano' (or a generic per-request payment callback) wired through one of the x402 Nano clients above, additive and default-compatible with existing billing.

Happy to draft a PR on the api-clients-automation path if the team is interested. I have not changed any billing or security primitives; this is additive and opt-in.