fix some broken links

docs/fundamentals-and-concepts/stellar-stack.mdx

@@ -39,7 +39,7 @@ The Soroban CLI is the command line interface to Soroban and can be downloaded [
 
 SDKs simplify some of the work of accessing Horizon and the Soroban RPC by converting the data into friendlier formats and allowing you to program in the language of your choice. Stellar’s SDKs show you how to request data and create and submit transactions. Soroban's SDKs allow you to write smart contracts in Rust and interact with smart contracts in a myriad of other languages.
 
-View Stellar's [SDK library](../tools/sdks.mdx) to access our SDKs and their documentation. View Soroban's [SDK library](https://soroban.stellar.org/docs/category/sdks) in the Soroban docs.
+View Stellar's [SDK library](../tools/sdks/README.mdx) to access our SDKs and their documentation. View Soroban's [SDK library](https://soroban.stellar.org/docs/category/sdks) in the Soroban docs.
 
 ## DeFi protocols
 

docs/run-core-node/index.mdx

@@ -7,7 +7,7 @@ import { Alert } from "@site/src/components/Alert";
 
 Stellar is a peer-to-peer network made up of nodes, which are computers that keep a common distributed [ledger](../fundamentals-and-concepts/stellar-data-structures/ledgers.mdx), and that communicate to validate and add [transactions](../fundamentals-and-concepts/stellar-data-structures/operations-and-transactions.mdx) to it. Nodes use a program called Stellar Core — an implementation of the [Stellar Consensus Protocol](../fundamentals-and-concepts/stellar-consensus-protocol.mdx) — to stay in sync as they work to agree on the validity of transaction sets and to apply them to the ledger. Generally, nodes reach consensus, apply a transaction set, and update the ledger every 3-5 seconds.
 
-You don’t need to run a node to build on Stellar: you can start developing with your [SDK of choice](../tools/sdks.mdx), and use public instances of Horizon to query the ledger and submit transactions right away. In fact, the Stellar Development Foundation offers two public instances of Horizon — one for the public network and one for the testnet — which you can read more about in our [API reference docs](https://developers.stellar.org/api). [Lobstr](https://horizon.stellar.lobstr.co), [Public Node](https://horizon.publicnode.org/), and [Coinqvest](https://horizon.stellar.coinqvest.com) also offer public Horizon instances.
+You don’t need to run a node to build on Stellar: you can start developing with your [SDK of choice](../tools/sdks/README.mdx), and use public instances of Horizon to query the ledger and submit transactions right away. In fact, the Stellar Development Foundation offers two public instances of Horizon — one for the public network and one for the testnet — which you can read more about in our [API reference docs](https://developers.stellar.org/api). [Lobstr](https://horizon.stellar.lobstr.co), [Public Node](https://horizon.publicnode.org/), and [Coinqvest](https://horizon.stellar.coinqvest.com) also offer public Horizon instances.
 
 Even if you _do_ want to run your [own instance of Horizon](../run-platform-server/index.mdx), it bundles its own version of Core and manages its lifetime entirely, so there's no need to run a standalone instance.
 

docs/tutorials/send-and-receive-payments.mdx

@@ -24,7 +24,7 @@ In the following code samples, proper error checking is omitted for brevity. How
 
 ## Send a Payment
 
-Stellar stores and communicates transaction data in a binary format called [XDR](../encyclopedia/xdr.mdx), which is optimized for network performance but unreadable to the human eye. Luckily, [Horizon](https://developers.stellar.org/api), the Stellar API, and the [Stellar SDKs](../tools/sdks.mdx) convert XDRs into friendlier formats. Here’s how you might send 10 lumens to an account:
+Stellar stores and communicates transaction data in a binary format called [XDR](../encyclopedia/xdr.mdx), which is optimized for network performance but unreadable to the human eye. Luckily, [Horizon](https://developers.stellar.org/api), the Stellar API, and the [Stellar SDKs](../tools/sdks/README.mdx) convert XDRs into friendlier formats. Here’s how you might send 10 lumens to an account:
 
 <CodeExample>