From 69c068f78a7e23e88b589fd564b1313310770168 Mon Sep 17 00:00:00 2001
From: Ake <10195782+akegaviar@users.noreply.github.com>
Date: Thu, 4 Jun 2026 16:18:21 +0800
Subject: [PATCH] docs: note archive-node requirement for MATIC_RPC_URL and
 expand provider list

Graph Node indexes from each subgraph's startBlock (some from 2020) and
issues historical eth_call requests while indexing (e.g. ERC-20 metadata
reads in fpmm-subgraph), which full/pruned nodes can't serve. Clarify that
an archive node is needed, note the value is the full https:// URL and where
it is consumed in docker-compose.yml, and round out the provider list.
---
 README.md | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 80e1703..a7e61cb 100644
--- a/README.md
+++ b/README.md
@@ -21,10 +21,12 @@
 Create a `.env` file with the following variables:
 
 ```bash
-MATIC_RPC_URL=
+MATIC_RPC_URL=https://your-polygon-rpc-endpoint
 ```
 
-Here, `MATIC_RPC_URL` should be your RPC URL for the Polygon network. Common providers include Alchemy and Infura.
+`MATIC_RPC_URL` is the full RPC URL (including the `https://` scheme) for **Polygon mainnet**. It's passed straight to Graph Node via `ethereum: 'matic:${MATIC_RPC_URL}'` in `docker-compose.yml`.
+
+Use an **archive node**. Graph Node replays history from each subgraph's `startBlock` (some reach back to 2020) and makes historical `eth_call` requests while indexing — for example, reading ERC-20 `name`/`symbol`/`decimals` in the fpmm-subgraph — which full or pruned nodes can't serve. Providers offering Polygon archive access include [Alchemy](https://www.alchemy.com/), [Chainstack](https://chainstack.com/), [Infura](https://www.infura.io/), and [QuickNode](https://www.quicknode.com/).
 
 ## Running the test suite