rustdoc

name	rustdoc
description	Look up Rust dependency API docs locally. Use when the user or task requires information about a dependency's API, types, traits, functions, or modules — e.g. "look up guppy's PackageGraph", "what methods does rustdoc_types::Item have", "show me clap's derive API".

Rustdoc Lookup

Consult locally-generated rustdoc HTML to look up API details from dependency crates. Use this whenever you need to know a type's fields, an enum's variants, a trait's methods, or a function's signature to complete a task — don't guess, look it up.

Instructions

Step 1: Identify the target

Determine what you need to look up:

• Crate name (required) — e.g. guppy, rustdoc-types, clap
• Item (optional) — a struct, enum, trait, function, module, or type alias

If the crate name is unclear, check Cargo.toml for available dependencies.

Step 2: Generate docs if needed

Run:

cargo doc -p <crate> --no-deps

This generates docs for just that crate (no transitive deps), which is fast.

Note: If cargo doc fails because the crate name isn't an exact match, check Cargo.toml or Cargo.lock for the correct package name.

Step 3: Find the right doc page

Crate names with hyphens become underscores in the doc path (e.g. rustdoc-types → rustdoc_types).

Use this file structure under target/doc/<crate_name>/:

Item kind	Path
Crate root	index.html
Struct	struct.<Name>.html
Enum	enum.<Name>.html
Trait	trait.<Name>.html
Function	fn.<Name>.html
Type alias	type.<Name>.html
Constant	constant.<Name>.html
Macro	macro.<Name>.html
Module	<module>/index.html
All items	all.html

If the exact item is unknown, use one of these discovery approaches:

1. Glob for matching files: target/doc/<crate_name>/struct.*.html
2. Read all.html for a full listing of all items in the crate

If the item is inside a submodule, the path nests: target/doc/<crate_name>/<module>/struct.<Name>.html

Re-exported items (same crate): Rustdoc generates the doc page at the re-export location, not the original definition site. For example, if a crate re-exports foo::bar::Baz as foo::Baz, the page lives at struct.Baz.html in the crate root, not under bar/. If a direct path based on the original module doesn't work:

1. Glob for the item name across all subdirectories: target/doc/<crate_name>/**/struct.<Name>.html
2. Read all.html — it lists every item with its actual doc path regardless of re-export structure

Re-exported items (from another crate): With --no-deps, items re-exported from a dependency crate won't have doc pages — only a link stub pointing to the source crate's docs, which weren't generated. If the page you need is missing:

1. Identify the source crate (the HTML will contain a cross-crate link like ../other_crate/struct.Name.html)
2. Generate docs for the source crate too: cargo doc -p <source_crate> --no-deps
3. Then read the page at target/doc/<source_crate>/struct.<Name>.html

Step 4: Read and extract what you need

Read the HTML doc page using the Read tool. Rustdoc HTML is structured enough to extract:

• Type/function signatures
• Doc comments and examples
• Method listings (for structs/enums/traits)
• Variant listings (for enums)
• Trait implementations

Extract only the information relevant to the task at hand, then proceed with your work.

Tips

• For large pages, use the offset and limit parameters on Read to focus on the relevant section.
• When exploring an unfamiliar crate, start with index.html or all.html and narrow down.