jump

Use jump to follow source identifiers to definitions in the workspace, installed dependencies, or the standard library. Because resolution starts from an occurrence in your source, a dependency jump lands in the version your project actually installs — the one your lockfile selected, not the latest release and not a remembered API.

Use when

You have a visible source occurrence and need its definition.
You need an API outline or implementation for a resolved target.

Do not use when

You know only a symbol name; use grep_definition.
You need the body of an already discovered handle; use extract.

Request

{"file":"/workspace/project/src/lib.rs","symbols":[["UserService",42],["McpError",67],["spawn_session",104]],"output_mode":"api"}

Batch related identifiers from the same file: each extra round trip costs a full agent turn, and one jump call resolves every symbol in the batch even when the definitions land in different files.

Parameters

Field	Required	Default / bounds
`file`	source form	Path; `file_path` is accepted as an alias.
`symbols`	source form	Entries are `[symbol_name, line]`; line is a 1-based integer.
`handles`	handle form	Registered handles; mutually exclusive with source fields.
`output_mode`	no	`api`; union: `api`, `implementation`.
`show_implementations`	no	`false`; enabling can be expensive for widely used traits/types.
`workspace_root`	no	Source form; only needed when multiple workspaces are active.

What it returns

Resolved definitions grouped by destination. api returns signatures, hierarchy, and declarations; implementation selects Code, falling back to Full, with inline type annotations. Missing outlines or code retain exact LSP-range fallbacks. Optional implementor/attached-implementation outlines are included when requested.

Example

Real output — jumping McpError from project code lands in the rmcp crate's source, in the local registry:

## ~/.cargo/registry/.../rmcp-3.1.2/src/model.rs

pub struct ErrorData {
    /// The error type that occurred (using standard JSON-RPC error codes)
    pub code: ErrorCode,
    /// A short description of the error. The message SHOULD be limited to a concise single sentence.
    pub message: Cow<'static, str>,
    /// Additional information about the error.
    pub data: Option<Value>,
}

The real fields of the version the lockfile resolved, read from its source — not from documentation and not from training data.

Common mistakes

Using a guessed line or symbol spelling that is not visible at that location.
Requesting implementation after api when one implementation request would suffice.
Enabling show_implementations for broad traits without needing the complete surface.

grep_definition finds definitions when no source occurrence is visible.
extract reads the body of an already resolved definition by handle.
hover returns the signature and documentation without navigating away.
show_usage walks the opposite direction: to consumers instead of the definition.

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