feat(docs): describe off-chain calls and mention exit code 11 for getters (#3314)

Author: novusnota

dev-docs/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Docs
+
+- Described off-chain calls and mention exit code 11 for getters: PR [#3314](https://github.com/tact-lang/tact/pull/3314)
+
 ## [1.6.13] - 2025-05-29
 
 ### Language features

docs/src/content/docs/book/exit-codes.mdx

@@ -374,7 +374,9 @@ contract DictPic {
 
 ### 11: "Unknown" error {#11}
 
-Described in the [TVM][tvm] docs as "Unknown error, may be thrown by user programs," although most commonly used for problems with queuing a message send or problems with [get-methods](https://docs.ton.org/develop/smart-contracts/guidelines/get-methods).
+Described in the [TVM][tvm] docs as "Unknown error, may be thrown by user programs," although most commonly used for problems with queuing a message send or problems with [getters](/book/functions#get).
+
+In particular, if you try to send an ill-formed message on-chain or to call a non-existent getter function off-chain, an exit code 11 will be thrown.
 
 ```tact
 try {

docs/src/content/docs/book/functions.mdx

@@ -533,6 +533,14 @@ contract AntiPositive() {
 }
 ```
 
+### Off-chain calls
+
+You can call getter functions off-chain by using either a [proxy HTTP API](https://docs.ton.org/v3/guidelines/dapps/apis-sdks/ton-http-apis) or a [secure ADNL API](https://docs.ton.org/v3/guidelines/dapps/apis-sdks/ton-adnl-apis) for direct connections to TON nodes. For your convenience, there are many [SDKs for various general-purpose programming languages](https://docs.ton.org/v3/guidelines/dapps/apis-sdks/sdk). And to call getter functions locally, use the Tact-generated [contract wrapper class](/book/debug#wrappers-contract).
+
+Notice that in those APIs and SDKs, getters are often referred to as _get methods_, as they are, in fact, callable methods of contracts that behave somewhat similarly to get methods in many object-oriented programming languages.
+
+If the contract is already deployed to the testnet or the mainnet, some TON Blockchain explorers allow you to call get methods directly from their interface, providing their names and input stack arguments. As with other ways of calling getters, if you try to call a non-existent getter, an [exit code 11](/book/exit-codes#11) will be thrown: `"Unknown" error`.
+
 ## `init` — constructor function {#init}
 
 <Badge text="Contract scope" variant="note" size="medium"/><p/>