Enum ErrorCode 

#[non_exhaustive]
pub enum ErrorCode {
    ParseError = -32_700,
    InvalidRequest = -32_600,
    MethodNotFound = -32_601,
    InvalidParams = -32_602,
    InternalError = -32_603,
    TaskNotFound = -32_001,
    TaskNotCancelable = -32_002,
    PushNotificationNotSupported = -32_003,
    UnsupportedOperation = -32_004,
    ContentTypeNotSupported = -32_005,
    InvalidAgentResponse = -32_006,
    ExtendedAgentCardNotConfigured = -32_007,
    ExtensionSupportRequired = -32_008,
    VersionNotSupported = -32_009,
}

Numeric error codes defined by JSON-RPC 2.0 and the A2A v1.0 specification.

JSON-RPC standard codes occupy the -32700 to -32600 range. A2A-specific codes occupy -32001 to -32099.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

ParseError = -32_700

Invalid JSON was received by the server (-32700).

InvalidRequest = -32_600

The JSON sent is not a valid Request object (-32600).

MethodNotFound = -32_601

The method does not exist or is not available (-32601).

InvalidParams = -32_602

Invalid method parameters (-32602).

InternalError = -32_603

Internal JSON-RPC error (-32603).

TaskNotFound = -32_001

The requested task was not found (-32001).

TaskNotCancelable = -32_002

The task cannot be canceled in its current state (-32002).

PushNotificationNotSupported = -32_003

The agent does not support push notifications (-32003).

UnsupportedOperation = -32_004

The requested operation is not supported by this agent (-32004).

ContentTypeNotSupported = -32_005

The requested content type is not supported (-32005).

InvalidAgentResponse = -32_006

The agent returned an invalid response (-32006).

ExtendedAgentCardNotConfigured = -32_007

Extended agent card not configured (-32007).

ExtensionSupportRequired = -32_008

A required extension is not supported (-32008).

VersionNotSupported = -32_009

The requested protocol version is not supported (-32009).

Implementations

impl ErrorCode

pub const fn as_i32(self) -> i32

Returns the numeric value of this error code.

pub const fn default_message(self) -> &'static str

Returns a short human-readable description of the code.

pub const fn a2a_reason(self) -> Option<&'static str>

Returns the A2A error reason in UPPER_SNAKE_CASE without the “Error” suffix, as required by the spec for google.rpc.ErrorInfo.reason.

Returns None for standard JSON-RPC errors (not A2A-specific).

pub const fn metric_label(self) -> &'static str

A bounded, low-cardinality label for use as a metric attribute.

Distinct from a2a_reason, which is None for standard JSON-RPC codes because the spec has no reason string for them. A metric label must exist for every code, or the errors a dashboard most needs to see — parse failures, internal errors — would be the ones missing from it.

Also distinct from default_message: messages are prose and may be reworded, while these are identifiers a dashboard query depends on. Changing one is a breaking change for whoever is alerting on it.

The set is closed and small — one label per variant — so it is safe to use directly as a metric dimension.

pub fn from_a2a_reason(reason: &str) -> Option<ErrorCode>

Resolves an UPPER_SNAKE_CASE A2A reason (as carried in google.rpc.ErrorInfo.reason) back to its ErrorCode.

The exact inverse of ErrorCode::a2a_reason; returns None for unknown reasons and for standard JSON-RPC codes (which have no A2A reason).

pub const fn http_status(self) -> u16

Returns the HTTP status code for this error, per Section 5.4 of the spec.

Provenance

These values are §5.4’s table as published at https://github.com/a2aproject/A2A/blob/main/docs/specification.md, re-read on 2026-08-30. Three of them changed from what this crate shipped before that date — TaskNotCancelable 409→400, ContentTypeNotSupported 415→400, and InvalidAgentResponse 502→500 — because the vendored copy of the specification in docs/implementation/v1.0.0-specification-complete.md was a snapshot taken 2026-03-31 and upstream has since amended the table in place, under the same 1.0.0 version string.

The drift was found by running this repository’s TCK against an agent built on the official Python SDK (a2a-sdk 1.1.2): the kit failed it for answering 400 where the kit expected 409, and the SDK was right. Nothing caught it earlier because the kit and this crate read the same stale table, so they agreed with each other — the symmetric misreading the TCK’s own README warns about.

Some of the statuses here are more natural than §5.4’s choice — 415 Unsupported Media Type says more than 400 about a bad Content-Type. Conformance is not a place to be more helpful than the specification: a client written against §5.4 matches on the code the table names, and a “better” status is one it does not recognise.

pub const fn grpc_status(self) -> &'static str

Returns the gRPC status code string for this error, per Section 5.4.

Trait Implementations

impl Clone for ErrorCode

fn clone(&self) -> ErrorCode

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for ErrorCode

impl Debug for ErrorCode

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ErrorCode

fn deserialize<__D>( __deserializer: __D, ) -> Result<ErrorCode, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for ErrorCode

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Eq for ErrorCode

impl Hash for ErrorCode

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for ErrorCode

fn eq(&self, other: &ErrorCode) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for ErrorCode

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ErrorCode

impl TryFrom<i32> for ErrorCode

type Error = i32

The type returned in the event of a conversion error.

fn try_from(v: i32) -> Result<ErrorCode, <ErrorCode as TryFrom<i32>>::Error>

Performs the conversion.