Enum BuildError 

#[non_exhaustive]
pub enum BuildError {
    DuplicateTool(String),
    InvalidToolName(String),
    MissingState {
        handler: String,
        type_name: &'static str,
    },
    InvalidResource {
        uri: String,
        reason: String,
    },
    DuplicateResource(String),
    DuplicatePrompt(String),
    InvalidPromptName(String),
    InvalidCompletion {
        owner: String,
        argument: String,
    },
    InvalidHeaderAnnotation {
        tool: String,
        reason: String,
    },
    InvalidExtension(String),
    InvalidLimit(&'static str),
    WeakRequestStateKey,
    RandomUnavailable(String),
    InvalidApp {
        uri: String,
        reason: String,
    },
    InvalidScope {
        handler: String,
        scope: String,
    },
    Serialize(&'static str, Error),
}

Errors detected while building a server.

Display gives the problem in one line; BuildError::help says how to fix it. Debug prints both, so fn main() -> Result<..> with .build()? shows the fix too.

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.

DuplicateTool(String)

Two tools share a name.

InvalidToolName(String)

A tool name breaks the specification’s naming rules.

MissingState

A handler needs shared state that was not registered.

Fields

handler: String

The tool or prompt name, or the resource URI.

type_name: &'static str

The missing type.

InvalidResource

A resource URI or URI template is invalid.

Fields

uri: String

The URI or URI template.

reason: String

What is wrong with it.

DuplicateResource(String)

Two resources share a URI, or two templates share a URI template.

DuplicatePrompt(String)

Two prompts share a name.

InvalidPromptName(String)

A prompt name is empty or contains control characters.

InvalidCompletion

A completion provider is attached to an unknown argument.

Fields

owner: String

The prompt name or URI template.

argument: String

The argument or template variable.

InvalidHeaderAnnotation

An x-mcp-header annotation breaks the specification’s constraints.

Fields

tool: String

The tool name.

reason: String

The violated constraint.

InvalidExtension(String)

An extension identifier is malformed or registered twice.

InvalidLimit(&'static str)

A limit is out of range.

WeakRequestStateKey

The requestState signing key is shorter than MIN_REQUEST_STATE_KEY_BYTES.

RandomUnavailable(String)

No random requestState key could be generated.

InvalidApp

An MCP Apps interface or a tool’s ui is invalid.

Fields

uri: String

The ui:// URI (or the tool name).

reason: String

What is wrong.

InvalidScope

A handler declares a malformed OAuth scope.

Fields

handler: String

The tool or prompt name, or the resource URI.

scope: String

The scope.

Serialize(&'static str, Error)

A pre-serialized response could not be built.

Implementations

impl BuildError

pub fn help(&self) -> String

How to fix the problem.

Trait Implementations

impl Debug for BuildError

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

Formats the value using the given formatter.

impl Display for BuildError

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

Formats the value using the given formatter.

impl Error for BuildError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.