Struct RequestMetaObject 

pub struct RequestMetaObject(pub MetaObject);

Available on crate features mcp and tools only.

The _meta map carried by requests (spec RequestMetaObject).

In addition to arbitrary extension keys, requests reserve:

• progressToken for progress tracking
• io.modelcontextprotocol/protocolVersion (SEP-2575)
• io.modelcontextprotocol/clientInfo (SEP-2575)
• io.modelcontextprotocol/clientCapabilities (SEP-2575)
• io.modelcontextprotocol/logLevel (SEP-2575)

The 2026-07-28 draft schema requires the protocol-version and client-capabilities keys; client-info is optional. Earlier protocol versions do not know them. All keys therefore stay optional at runtime and in the generated (version-shared) JSON schema — use RequestMetaObject::missing_required_keys to validate a request against the negotiated protocol version.

This type dereferences to MetaObject (and transitively to the underlying map), so general helpers such as the SEP-414 trace-context accessors remain available.

Tuple Fields

0: MetaObject

Implementations

impl RequestMetaObject

pub const DRAFT_REQUIRED_KEYS: [&'static str; 2]

Request _meta keys the 2026-07-28 draft schema marks as required.

pub fn new() -> RequestMetaObject

Create an empty request metadata map.

pub fn with_progress_token(token: ProgressToken) -> RequestMetaObject

Create a new request meta with a progress token set

pub fn with_client_context( protocol_version: ProtocolVersion, client_info: Implementation, client_capabilities: ClientCapabilities, ) -> RequestMetaObject

Create request metadata with the client context SEP-2575 requires on every request.

pub fn get_progress_token(&self) -> Option<ProgressToken>

Get the progress token carried in _meta, if present and valid.

pub fn set_progress_token(&mut self, token: ProgressToken)

Set the progress token carried in _meta.

pub fn protocol_version(&self) -> Option<ProtocolVersion>

Get the MCP protocol version carried in _meta, if present and valid.

pub fn set_protocol_version(&mut self, protocol_version: ProtocolVersion)

Set the MCP protocol version carried in _meta.

pub fn client_info(&self) -> Option<Implementation>

Get the client implementation identity carried in _meta, if present and valid.

pub fn set_client_info(&mut self, client_info: Implementation)

Set the client implementation identity carried in _meta.

pub fn client_capabilities(&self) -> Option<ClientCapabilities>

Get the client capabilities carried in _meta, if present and valid.

pub fn set_client_capabilities( &mut self, client_capabilities: ClientCapabilities, )

Set the client capabilities carried in _meta.

pub fn log_level(&self) -> Option<LoggingLevel>

Get the requested per-request log level carried in _meta, if present and valid.

pub fn set_log_level(&mut self, log_level: LoggingLevel)

Set the requested per-request log level carried in _meta.

pub fn missing_required_keys( &self, protocol_version: &ProtocolVersion, ) -> Vec<&'static str>

Return the Self::DRAFT_REQUIRED_KEYS whose values are absent or invalid in this map, if protocol_version requires them.

A key counts as missing when it is not present or when its value does not decode into the expected type (e.g. a numeric protocolVersion or a string clientInfo), matching what the typed accessors return.

Protocol versions before 2026-07-28 have no required request metadata, so this always returns an empty list for them.

Examples

use rmcp::model::{ProtocolVersion, RequestMetaObject};

let meta = RequestMetaObject::new();
// Older protocols have no required request metadata.
assert!(
    meta.missing_required_keys(&ProtocolVersion::V_2025_11_25)
        .is_empty()
);
// The 2026-07-28 protocol requires per-request context.
assert_eq!(
    meta.missing_required_keys(&ProtocolVersion::V_2026_07_28),
    RequestMetaObject::DRAFT_REQUIRED_KEYS.to_vec(),
);

pub fn extend(&mut self, other: RequestMetaObject)

Insert every entry of other, overwriting existing keys on conflict.

Methods from Deref<Target = MetaObject>

pub fn get_traceparent(&self) -> Option<&str>

Get the W3C traceparent value (SEP-414), if present.

pub fn set_traceparent(&mut self, value: impl Into<String>)

Set the W3C traceparent value (SEP-414).

use rmcp::model::MetaObject;

let mut meta = MetaObject::new();
meta.set_traceparent("00-0af7651916cd43dd8448eb211c80319c-00f067aa0ba902b7-01");
assert_eq!(
    meta.get_traceparent(),
    Some("00-0af7651916cd43dd8448eb211c80319c-00f067aa0ba902b7-01"),
);

pub fn get_tracestate(&self) -> Option<&str>

Get the W3C tracestate value (SEP-414), if present.

pub fn set_tracestate(&mut self, value: impl Into<String>)

Set the W3C tracestate value (SEP-414).

pub fn get_baggage(&self) -> Option<&str>

Get the W3C baggage value (SEP-414), if present.

pub fn set_baggage(&mut self, value: impl Into<String>)

Set the W3C baggage value (SEP-414).

pub fn extend(&mut self, other: MetaObject)

Insert every entry of other, overwriting existing keys on conflict.

Methods from Deref<Target = Map<String, Value>>

pub fn clear(&mut self)

Clears the map, removing all values.

pub fn get<Q>(&self, key: &Q) -> Option<&Value>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn contains_key<Q>(&self, key: &Q) -> bool

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Returns true if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut Value>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Returns a mutable reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn get_key_value<Q>(&self, key: &Q) -> Option<(&String, &Value)>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Returns the key-value pair matching the given key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn insert(&mut self, k: String, v: Value) -> Option<Value>

Inserts a key-value pair into the map.

If the map did not have this key present, None is returned.

If the map did have this key present, the value is updated, and the old value is returned.

pub fn shift_insert( &mut self, index: usize, k: String, v: Value, ) -> Option<Value>

Available on crate feature preserve_order only.

Insert a key-value pair in the map at the given index.

If the map did not have this key present, None is returned.

If the map did have this key present, the key is moved to the new position, the value is updated, and the old value is returned.

pub fn remove<Q>(&mut self, key: &Q) -> Option<Value>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Removes a key from the map, returning the value at the key if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

If serde_json’s “preserve_order” is enabled, .remove(key) is equivalent to .swap_remove(key), replacing this entry’s position with the last element. If you need to preserve the relative order of the keys in the map, use .shift_remove(key) instead.

pub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(String, Value)>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Removes a key from the map, returning the stored key and value if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

If serde_json’s “preserve_order” is enabled, .remove_entry(key) is equivalent to .swap_remove_entry(key), replacing this entry’s position with the last element. If you need to preserve the relative order of the keys in the map, use .shift_remove_entry(key) instead.

pub fn swap_remove<Q>(&mut self, key: &Q) -> Option<Value>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Available on crate feature preserve_order only.

Removes and returns the value corresponding to the key from the map.

Like Vec::swap_remove, the entry is removed by swapping it with the last element of the map and popping it off. This perturbs the position of what used to be the last element!

pub fn swap_remove_entry<Q>(&mut self, key: &Q) -> Option<(String, Value)>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Available on crate feature preserve_order only.

Remove and return the key-value pair.

Like Vec::swap_remove, the entry is removed by swapping it with the last element of the map and popping it off. This perturbs the position of what used to be the last element!

pub fn shift_remove<Q>(&mut self, key: &Q) -> Option<Value>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Available on crate feature preserve_order only.

Removes and returns the value corresponding to the key from the map.

Like Vec::remove, the entry is removed by shifting all of the elements that follow it, preserving their relative order. This perturbs the index of all of those elements!

pub fn shift_remove_entry<Q>(&mut self, key: &Q) -> Option<(String, Value)>

where String: Borrow<Q>, Q: Ord + Eq + Hash + ?Sized,

Available on crate feature preserve_order only.

Remove and return the key-value pair.

Like Vec::remove, the entry is removed by shifting all of the elements that follow it, preserving their relative order. This perturbs the index of all of those elements!

pub fn append(&mut self, other: &mut Map<String, Value>)

Moves all elements from other into self, leaving other empty.

pub fn entry<S>(&mut self, key: S) -> Entry<'_>

where S: Into<String>,

Gets the given key’s corresponding entry in the map for in-place manipulation.

pub fn len(&self) -> usize

Returns the number of elements in the map.

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

pub fn iter(&self) -> Iter<'_>

Gets an iterator over the entries of the map.

pub fn iter_mut(&mut self) -> IterMut<'_>

Gets a mutable iterator over the entries of the map.

pub fn keys(&self) -> Keys<'_>

Gets an iterator over the keys of the map.

pub fn values(&self) -> Values<'_>

Gets an iterator over the values of the map.

pub fn values_mut(&mut self) -> ValuesMut<'_>

Gets an iterator over mutable values of the map.

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&String, &mut Value) -> bool,

Retains only the elements specified by the predicate.

In other words, remove all pairs (k, v) such that f(&k, &mut v) returns false.

pub fn sort_keys(&mut self)

Sorts this map’s entries in-place using str’s usual ordering.

If serde_json’s “preserve_order” feature is not enabled, this method does no work because all JSON maps are always kept in a sorted state.

If serde_json’s “preserve_order” feature is enabled, this method destroys the original source order or insertion order of this map in favor of an alphanumerical order that matches how a BTreeMap with the same contents would be ordered. This takes O(n log n + c) time where n is the length of the map and c is the capacity.

Other maps nested within the values of this map are not sorted. If you need the entire data structure to be sorted at all levels, you must also call map.values_mut().for_each(Value::sort_all_objects).

Trait Implementations

impl Clone for RequestMetaObject

fn clone(&self) -> RequestMetaObject

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for RequestMetaObject

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

Formats the value using the given formatter.

impl Default for RequestMetaObject

fn default() -> RequestMetaObject

Returns the “default value” for a type.

impl Deref for RequestMetaObject

type Target = MetaObject

The resulting type after dereferencing.

fn deref(&self) -> &<RequestMetaObject as Deref>::Target

Dereferences the value.

impl DerefMut for RequestMetaObject

fn deref_mut(&mut self) -> &mut <RequestMetaObject as Deref>::Target

Mutably dereferences the value.

impl<'de> Deserialize<'de> for RequestMetaObject

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl From<Map<String, Value>> for RequestMetaObject

fn from(object: Map<String, Value>) -> RequestMetaObject

Converts to this type from the input type.

impl From<MetaObject> for RequestMetaObject

fn from(meta: MetaObject) -> RequestMetaObject

Converts to this type from the input type.

impl<C> FromContextPart<C> for RequestMetaObject

where C: AsRequestContext,

fn from_context_part(context: &mut C) -> Result<RequestMetaObject, ErrorData>

impl JsonSchema for RequestMetaObject

Available on crate feature schemars only.

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

impl PartialEq for RequestMetaObject

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for RequestMetaObject

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 RequestMetaObject