agent_client_protocol_schema/v2/
error.rs

1//! Error handling for the Agent Client Protocol.
2//!
3//! This module provides error types and codes following the JSON-RPC 2.0 specification,
4//! with additional protocol-specific error codes for authentication and other ACP-specific scenarios.
5//!
6//! All methods in the protocol follow standard JSON-RPC 2.0 error handling:
7//! - Successful responses include a `result` field
8//! - Errors include an `error` object with `code` and `message`
9//! - Notifications never receive responses (success or error)
10//!
11//! See: [Error Handling](https://agentclientprotocol.com/protocol/overview#error-handling)
12
13use std::{fmt::Display, str};
14
15use schemars::{JsonSchema, Schema};
16use serde::{Deserialize, Serialize};
17use serde_with::{DefaultOnError, serde_as, skip_serializing_none};
18
19use crate::IntoOption;
20
21/// Convenience result type using this protocol version's error type.
22pub type Result<T, E = Error> = std::result::Result<T, E>;
23
24/// JSON-RPC error object.
25///
26/// Represents an error that occurred during method execution, following the
27/// JSON-RPC 2.0 error object specification with optional additional data.
28///
29/// See protocol docs: [JSON-RPC Error Object](https://www.jsonrpc.org/specification#error_object)
30#[serde_as]
31#[skip_serializing_none]
32#[derive(Debug, Clone, Serialize, Deserialize, JsonSchema, PartialEq, Eq)]
33#[non_exhaustive]
34pub struct Error {
35    /// A number indicating the error type that occurred.
36    /// This must be an integer as defined in the JSON-RPC specification.
37    pub code: ErrorCode,
38    /// A string providing a short description of the error.
39    /// The message should be limited to a concise single sentence.
40    pub message: String,
41    /// Optional primitive or structured value that contains additional information about the error.
42    /// This may include debugging information or context-specific details.
43    #[serde_as(deserialize_as = "DefaultOnError")]
44    #[schemars(extend("x-deserialize-default-on-error" = true))]
45    #[serde(default)]
46    pub data: Option<serde_json::Value>,
47}
48
49impl Error {
50    /// Creates a new error with the given code and message.
51    ///
52    /// The code parameter can be an `ErrorCode` constant or a tuple of (code, message).
53    #[must_use]
54    pub fn new(code: i32, message: impl Into<String>) -> Self {
55        Error {
56            code: code.into(),
57            message: message.into(),
58            data: None,
59        }
60    }
61
62    /// Adds additional data to the error.
63    ///
64    /// This method is chainable and allows attaching context-specific information
65    /// to help with debugging or provide more details about the error.
66    #[must_use]
67    pub fn data(mut self, data: impl IntoOption<serde_json::Value>) -> Self {
68        self.data = data.into_option();
69        self
70    }
71
72    /// Invalid JSON was received by the server. An error occurred on the server while parsing the JSON text.
73    #[must_use]
74    pub fn parse_error() -> Self {
75        ErrorCode::ParseError.into()
76    }
77
78    /// The JSON sent is not a valid Request object.
79    #[must_use]
80    pub fn invalid_request() -> Self {
81        ErrorCode::InvalidRequest.into()
82    }
83
84    /// The method does not exist / is not available.
85    #[must_use]
86    pub fn method_not_found() -> Self {
87        ErrorCode::MethodNotFound.into()
88    }
89
90    /// Invalid method parameter(s).
91    #[must_use]
92    pub fn invalid_params() -> Self {
93        ErrorCode::InvalidParams.into()
94    }
95
96    /// Internal JSON-RPC error.
97    #[must_use]
98    pub fn internal_error() -> Self {
99        ErrorCode::InternalError.into()
100    }
101
102    /// Request was cancelled.
103    ///
104    /// Execution of the method was aborted either due to a cancellation request from the caller
105    /// or because of resource constraints or shutdown.
106    #[must_use]
107    pub fn request_cancelled() -> Self {
108        ErrorCode::RequestCancelled.into()
109    }
110
111    /// Authentication required.
112    #[must_use]
113    pub fn auth_required() -> Self {
114        ErrorCode::AuthRequired.into()
115    }
116
117    /// **UNSTABLE**
118    ///
119    /// This capability is not part of the spec yet, and may be removed or changed at any point.
120    ///
121    /// The agent requires user input via a URL-based elicitation before it can proceed.
122    #[cfg(feature = "unstable_elicitation")]
123    #[must_use]
124    pub fn url_elicitation_required() -> Self {
125        ErrorCode::UrlElicitationRequired.into()
126    }
127
128    /// A given resource, such as a file, was not found.
129    #[must_use]
130    pub fn resource_not_found(uri: Option<String>) -> Self {
131        let err: Self = ErrorCode::ResourceNotFound.into();
132        if let Some(uri) = uri {
133            err.data(serde_json::json!({ "uri": uri }))
134        } else {
135            err
136        }
137    }
138
139    /// Converts a standard error into an internal JSON-RPC error.
140    ///
141    /// The error's string representation is included as additional data.
142    #[must_use]
143    pub fn into_internal_error(err: impl std::error::Error) -> Self {
144        Error::internal_error().data(err.to_string())
145    }
146}
147
148/// Predefined error codes for common JSON-RPC and ACP-specific errors.
149///
150/// These codes follow the JSON-RPC 2.0 specification for standard errors
151/// and use the reserved range (-32000 to -32099) for protocol-specific errors.
152#[derive(Clone, Copy, Deserialize, Eq, JsonSchema, PartialEq, Serialize, strum::Display)]
153#[cfg_attr(test, derive(strum::EnumIter))]
154#[serde(from = "i32", into = "i32")]
155#[schemars(!from, !into)]
156#[non_exhaustive]
157pub enum ErrorCode {
158    // Standard errors
159    /// Invalid JSON was received by the server.
160    /// An error occurred on the server while parsing the JSON text.
161    #[schemars(transform = error_code_transform)]
162    #[strum(to_string = "Parse error")]
163    ParseError, // -32700
164    /// The JSON sent is not a valid Request object.
165    #[schemars(transform = error_code_transform)]
166    #[strum(to_string = "Invalid request")]
167    InvalidRequest, // -32600
168    /// The method does not exist or is not available.
169    #[schemars(transform = error_code_transform)]
170    #[strum(to_string = "Method not found")]
171    MethodNotFound, // -32601
172    /// Invalid method parameter(s).
173    #[schemars(transform = error_code_transform)]
174    #[strum(to_string = "Invalid params")]
175    InvalidParams, // -32602
176    /// Internal JSON-RPC error.
177    /// Reserved for implementation-defined server errors.
178    #[schemars(transform = error_code_transform)]
179    #[strum(to_string = "Internal error")]
180    InternalError, // -32603
181    /// Execution of the method was aborted either due to a cancellation request from the caller or
182    /// because of resource constraints or shutdown.
183    #[schemars(transform = error_code_transform)]
184    #[strum(to_string = "Request cancelled")]
185    RequestCancelled, // -32800
186
187    // Custom errors
188    /// Authentication is required before this operation can be performed.
189    #[schemars(transform = error_code_transform)]
190    #[strum(to_string = "Authentication required")]
191    AuthRequired, // -32000
192    /// A given resource, such as a file, was not found.
193    #[schemars(transform = error_code_transform)]
194    #[strum(to_string = "Resource not found")]
195    ResourceNotFound, // -32002
196    #[cfg(feature = "unstable_elicitation")]
197    /// **UNSTABLE**
198    ///
199    /// This capability is not part of the spec yet, and may be removed or changed at any point.
200    ///
201    /// The agent requires user input via a URL-based elicitation before it can proceed.
202    #[schemars(transform = error_code_transform)]
203    #[strum(to_string = "URL elicitation required")]
204    UrlElicitationRequired, // -32042
205
206    /// Other undefined error code.
207    #[schemars(untagged)]
208    #[strum(to_string = "Unknown error")]
209    Other(i32),
210}
211
212impl From<i32> for ErrorCode {
213    fn from(value: i32) -> Self {
214        match value {
215            -32700 => ErrorCode::ParseError,
216            -32600 => ErrorCode::InvalidRequest,
217            -32601 => ErrorCode::MethodNotFound,
218            -32602 => ErrorCode::InvalidParams,
219            -32603 => ErrorCode::InternalError,
220            -32800 => ErrorCode::RequestCancelled,
221            -32000 => ErrorCode::AuthRequired,
222            -32002 => ErrorCode::ResourceNotFound,
223            #[cfg(feature = "unstable_elicitation")]
224            -32042 => ErrorCode::UrlElicitationRequired,
225            _ => ErrorCode::Other(value),
226        }
227    }
228}
229
230impl From<ErrorCode> for i32 {
231    fn from(value: ErrorCode) -> Self {
232        match value {
233            ErrorCode::ParseError => -32700,
234            ErrorCode::InvalidRequest => -32600,
235            ErrorCode::MethodNotFound => -32601,
236            ErrorCode::InvalidParams => -32602,
237            ErrorCode::InternalError => -32603,
238            ErrorCode::RequestCancelled => -32800,
239            ErrorCode::AuthRequired => -32000,
240            ErrorCode::ResourceNotFound => -32002,
241            #[cfg(feature = "unstable_elicitation")]
242            ErrorCode::UrlElicitationRequired => -32042,
243            ErrorCode::Other(value) => value,
244        }
245    }
246}
247
248impl std::fmt::Debug for ErrorCode {
249    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
250        write!(f, "{}: {self}", i32::from(*self))
251    }
252}
253
254fn error_code_transform(schema: &mut Schema) {
255    let name = schema
256        .get("const")
257        .expect("Unexpected schema for ErrorCode")
258        .as_str()
259        .expect("unexpected type for schema");
260    let code = match name {
261        "ParseError" => ErrorCode::ParseError,
262        "InvalidRequest" => ErrorCode::InvalidRequest,
263        "MethodNotFound" => ErrorCode::MethodNotFound,
264        "InvalidParams" => ErrorCode::InvalidParams,
265        "InternalError" => ErrorCode::InternalError,
266        "RequestCancelled" => ErrorCode::RequestCancelled,
267        "AuthRequired" => ErrorCode::AuthRequired,
268        "ResourceNotFound" => ErrorCode::ResourceNotFound,
269        #[cfg(feature = "unstable_elicitation")]
270        "UrlElicitationRequired" => ErrorCode::UrlElicitationRequired,
271        _ => panic!("Unexpected error code name {name}"),
272    };
273    let mut description = schema
274        .get("description")
275        .expect("Missing description")
276        .as_str()
277        .expect("Unexpected type for description")
278        .to_owned();
279    schema.insert("title".into(), code.to_string().into());
280    description.insert_str(0, &format!("**{code}**: "));
281    schema.insert("description".into(), description.into());
282    schema.insert("const".into(), i32::from(code).into());
283    schema.insert("type".into(), "integer".into());
284    schema.insert("format".into(), "int32".into());
285}
286
287impl From<ErrorCode> for Error {
288    fn from(error_code: ErrorCode) -> Self {
289        Error::new(error_code.into(), error_code.to_string())
290    }
291}
292
293impl std::error::Error for Error {}
294
295impl Display for Error {
296    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
297        if self.message.is_empty() {
298            write!(f, "{}", i32::from(self.code))?;
299        } else {
300            write!(f, "{}", self.message)?;
301        }
302
303        if let Some(data) = &self.data {
304            let pretty = serde_json::to_string_pretty(data).unwrap_or_else(|_| data.to_string());
305            write!(f, ": {pretty}")?;
306        }
307
308        Ok(())
309    }
310}
311
312impl From<anyhow::Error> for Error {
313    fn from(error: anyhow::Error) -> Self {
314        match error.downcast::<Self>() {
315            Ok(error) => error,
316            Err(error) => Error::into_internal_error(&*error),
317        }
318    }
319}
320
321impl From<serde_json::Error> for Error {
322    fn from(error: serde_json::Error) -> Self {
323        Error::invalid_params().data(error.to_string())
324    }
325}
326
327#[cfg(test)]
328mod tests {
329    use strum::IntoEnumIterator;
330
331    use super::*;
332
333    #[test]
334    fn serialize_error_code() {
335        assert_eq!(
336            serde_json::from_value::<ErrorCode>(serde_json::json!(-32700)).unwrap(),
337            ErrorCode::ParseError
338        );
339        assert_eq!(
340            serde_json::to_value(ErrorCode::ParseError).unwrap(),
341            serde_json::json!(-32700)
342        );
343
344        assert_eq!(
345            serde_json::from_value::<ErrorCode>(serde_json::json!(1)).unwrap(),
346            ErrorCode::Other(1)
347        );
348        assert_eq!(
349            serde_json::to_value(ErrorCode::Other(1)).unwrap(),
350            serde_json::json!(1)
351        );
352    }
353
354    #[test]
355    fn serialize_error_code_equality() {
356        // Make sure this doesn't panic
357        let _schema = schemars::schema_for!(ErrorCode);
358        for error in ErrorCode::iter() {
359            assert_eq!(
360                error,
361                serde_json::from_value(serde_json::to_value(error).unwrap()).unwrap()
362            );
363        }
364    }
365}
agent_client_protocol_schema/v2/error.rs

agent_client_protocol_schema/v2/
error.rs
