Enum Block 

pub enum Block {
    Text {
        id: String,
        text: String,
    },
    Fields {
        id: String,
        items: Vec<Field>,
    },
    Table {
        id: String,
        columns: Vec<String>,
        rows: Vec<Vec<Value>>,
        offset: Option<u64>,
        total: Option<u64>,
    },
    List {
        id: String,
        items: Vec<Value>,
        ordered: Option<bool>,
        offset: Option<u64>,
        total: Option<u64>,
    },
    Custom {
        id: String,
        payload: Value,
    },
    Notice {
        id: String,
        severity: Severity,
        text: String,
    },
    Media {
        id: String,
        mime_type: String,
        url: String,
        alt: Option<String>,
    },
}

One semantic block. The id is assigned by the library (constructors leave it empty; it is filled in when the block is inserted into a window).

Note: this enum deliberately uses internal tagging #[serde(tag = "type")] — this is the wire format mandated by MCP GUI Bridge protocol §4.4 ({"type":"text","id":...,"text":...}). It cannot use serde’s default external tagging without violating the protocol and breaking agent interop. This is the single documented exception to the the repo’s docs/code-style.md “no tag="type"” rule (that rule targets WASM binary size and does not apply to this server crate).

Variants

Text

A paragraph of text.

Fields

id: String

Block id (library-assigned).

text: String

The text content.

Fields

A group of key/value fields.

Fields

id: String

Block id (library-assigned).

items: Vec<Field>

The field items.

Table

A table.

Fields

id: String

Block id (library-assigned).

columns: Vec<String>

Column headers, left to right.

rows: Vec<Vec<Value>>

Row data; rows[i][j] aligns with columns[j].

offset: Option<u64>

Offset of the first row when truncated (§9); defaults to absent (0).

total: Option<u64>

Total row count when truncated (§9).

List

A list.

Fields

id: String

Block id (library-assigned).

items: Vec<Value>

List items.

ordered: Option<bool>

true for an ordered list.

offset: Option<u64>

Offset of the first item when truncated (§9).

total: Option<u64>

Total item count when truncated (§9).

Custom

A fallback block carrying an arbitrary structured payload.

Fields

id: String

Block id (library-assigned).

payload: Value

Arbitrary payload.

Notice

A status / notice block.

Fields

id: String

Block id (library-assigned).

severity: Severity

Severity level.

text: String

Notice text.

Media

Read-side rich media: an image / screenshot / chart.

Fields

id: String

Block id (library-assigned).

mime_type: String

MIME type, e.g. image/png.

url: String

Where to fetch it: an https://, file://, or inline data:<mime>;base64,… URL.

alt: Option<String>

Text description — the semantic fallback for the agent.

Implementations

impl Block

pub fn text(text: impl Into<String>) -> Block

Build a text block.

pub fn fields<I, F>(items: I) -> Block

where I: IntoIterator<Item = F>, F: Into<Field>,

Build a fields block from any iterable of items convertible to Field.

pub fn table<C, R, Row, Cell>(columns: C, rows: R) -> Block

where C: IntoIterator<Item = Cell>, Cell: Into<String>, R: IntoIterator<Item = Row>, Row: IntoIterator, <Row as IntoIterator>::Item: Serialize,

Build a table block. Cells accept any Serialize.

pub fn table_truncated<C, R, Row, Cell>( columns: C, rows: R, offset: u64, total: u64, ) -> Block

where C: IntoIterator<Item = Cell>, Cell: Into<String>, R: IntoIterator<Item = Row>, Row: IntoIterator, <Row as IntoIterator>::Item: Serialize,

Build a truncated table block (§9): rows is the shown window, starting at offset, out of total rows overall.

pub fn list<I, T>(items: I) -> Block

where I: IntoIterator<Item = T>, T: Serialize,

Build an unordered list block. Items accept any Serialize.

pub fn ordered_list<I, T>(items: I) -> Block

where I: IntoIterator<Item = T>, T: Serialize,

Build an ordered list block. Items accept any Serialize.

pub fn list_truncated<I, T>( items: I, ordered: bool, offset: u64, total: u64, ) -> Block

where I: IntoIterator<Item = T>, T: Serialize,

Build a truncated list block (§9): items is the shown window, starting at offset, out of total items overall. ordered selects an ordered (1. 2. 3.) or unordered list.

pub fn notice(severity: Severity, text: impl Into<String>) -> Block

Build a notice block.

pub fn custom(payload: impl Serialize) -> Block

Build a custom block. The payload accepts any Serialize.

pub fn media(mime_type: impl Into<String>, url: impl Into<String>) -> Block

Build a media block (read-side rich media: image / screenshot / chart). url may be https://, file://, or an inline data:<mime>;base64,… URL; alt starts empty (set it via the handle).

Trait Implementations

impl Clone for Block

fn clone(&self) -> Block

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Block

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

Formats the value using the given formatter.

impl Serialize for Block

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.