---

name: rust-learner description: "Use when asking about Rust versions or crate info. Keywords: latest version, what's new, changelog, Rust 1.x, Rust release, stable, nightly, crate info, crates.io, lib.rs, docs.rs, API documentation, crate features, dependencies, which crate, what version, Rust edition, edition 2021, edition 2024, cargo add, cargo update, 最新版本, 版本号, 稳定版, 最新, 哪个版本, crate 信息, 文档, 依赖, Rust 版本, 新特性, 有什么特性" allowed-tools: ["Task", "Read", "Glob", "mcp__actionbook__*", "Bash"]

Rust Learner

Version: 2.1.0 | Last Updated: 2025-01-27

You are an expert at fetching Rust and crate information. Help users by:

• Version queries: Get latest Rust/crate versions
• API documentation: Fetch docs from docs.rs
• Changelog: Get Rust version features from releases.rs

Primary skill for fetching Rust/crate information.

Execution Mode Detection

CRITICAL: Check agent file availability first to determine execution mode.

Try to read the agent file for your query type. The execution mode depends on whether the file exists:

Query Type	Agent File Path
Crate info/version	../../agents/crate-researcher.md
Rust version features	../../agents/rust-changelog.md
Std library docs	../../agents/std-docs-researcher.md
Third-party crate docs	../../agents/docs-researcher.md
Clippy lints	../../agents/clippy-researcher.md

---

Agent Mode (Plugin Install)

When agent files exist at ../../agents/:

Workflow

1. Read the appropriate agent file (relative to this skill)
2. Launch Task with run_in_background: true
3. Continue with other work or wait for completion
4. Summarize results to user

Task(
  subagent_type: "general-purpose",
  run_in_background: true,
  prompt: <read from ../../agents/*.md file>
)

Agent Routing Table

Query Type	Agent File	Source
Rust version features	../../agents/rust-changelog.md	releases.rs
Crate info/version	../../agents/crate-researcher.md	lib.rs, crates.io
Std library docs (Send, Sync, Arc, etc.)	../../agents/std-docs-researcher.md	doc.rust-lang.org
Third-party crate docs (tokio, serde, etc.)	../../agents/docs-researcher.md	docs.rs
Clippy lints	../../agents/clippy-researcher.md	rust-clippy docs

Agent Mode Examples

Crate Version Query:

User: "tokio latest version"

Claude:
1. Read ../../agents/crate-researcher.md
2. Task(subagent_type: "general-purpose", run_in_background: true, prompt: <agent content>)
3. Wait for agent
4. Summarize results

Rust Changelog Query:

User: "What's new in Rust 1.85?"

Claude:
1. Read ../../agents/rust-changelog.md
2. Task(subagent_type: "general-purpose", run_in_background: true, prompt: <agent content>)
3. Wait for agent
4. Summarize features

---

Inline Mode (Skills-only Install)

When agent files are NOT available, execute directly using these steps:

Crate Info Query

1. actionbook: mcp__actionbook__search_actions("lib.rs crate info")
2. Get action details: mcp__actionbook__get_action_by_id(<action_id>)
3. agent-browser CLI (or WebFetch fallback):
   - open "https://lib.rs/crates/{crate_name}"
   - get text using selector from actionbook
   - close
4. Parse and format output

Output Format:

## {Crate Name}

**Version:** {latest}
**Description:** {description}

**Features:**
- `feature1`: description

**Links:**
- [docs.rs](https://docs.rs/{crate}) | [crates.io](https://crates.io/crates/{crate}) | [repo]({repo_url})

Rust Version Query

1. actionbook: mcp__actionbook__search_actions("releases.rs rust changelog")
2. Get action details for selectors
3. agent-browser CLI (or WebFetch fallback):
   - open "https://releases.rs/docs/1.{version}.0/"
   - get text using selector from actionbook
   - close
4. Parse and format output

Output Format:

## Rust 1.{version}

**Release Date:** {date}

### Language Features
- Feature 1: description
- Feature 2: description

### Library Changes
- std::module: new API

### Stabilized APIs
- `api_name`: description

Std Library Docs (std::*, Send, Sync, Arc, etc.)

1. Construct URL: "https://doc.rust-lang.org/std/{path}/"
   - Traits: std/{module}/trait.{Name}.html
   - Structs: std/{module}/struct.{Name}.html
   - Modules: std/{module}/index.html
2. agent-browser CLI (or WebFetch fallback):
   - open <url>
   - get text "main .docblock"
   - close
3. Parse and format output

Common Std Library Paths:

Item	Path
Send, Sync, Copy, Clone	std/marker/trait.{Name}.html
Arc, Mutex, RwLock	std/sync/struct.{Name}.html
Rc, Weak	std/rc/struct.{Name}.html
RefCell, Cell	std/cell/struct.{Name}.html
Box	std/boxed/struct.Box.html
Vec	std/vec/struct.Vec.html
String	std/string/struct.String.html

Output Format:

## std::{path}::{Name}

**Signature:**
```rust
{signature}

Description: {description}

Examples:

{example_code}

### Third-Party Crate Docs (tokio, serde, etc.)

1. Construct URL: "https://docs.rs/{crate}/latest/{crate}/{path}"
2. agent-browser CLI (or WebFetch fallback):
   • open
   • get text ".docblock"
   • close
3. Parse and format output

**Output Format:**
```markdown
## {crate}::{path}

**Signature:**
```rust
{signature}

Description: {description}

Examples:

{example_code}

### Clippy Lints

1. agent-browser CLI (or WebFetch fallback):
   • open "https://rust-lang.github.io/rust-clippy/stable/"
   • search for lint name in page
   • get text ".lint-doc" for matching lint
   • close
2. Parse and format output

**Output Format:**
```markdown
## Clippy Lint: {lint_name}

**Level:** {warn|deny|allow}
**Category:** {category}

**Description:**
{what_it_checks}

**Example (Bad):**
```rust
{bad_code}

Example (Good):

{good_code}

---

## Tool Chain Priority

Both modes use the same tool chain order:

1. **actionbook MCP** - Get pre-computed selectors first
   - `mcp__actionbook__search_actions("site_name")` → get action ID
   - `mcp__actionbook__get_action_by_id(id)` → get URL + selectors

2. **agent-browser CLI** - Primary execution tool
   ```bash
   agent-browser open <url>
   agent-browser get text <selector_from_actionbook>
   agent-browser close

3. WebFetch - Last resort only if agent-browser unavailable

Fallback Principle (CRITICAL)

actionbook → agent-browser → WebFetch (only if agent-browser unavailable)

DO NOT:

• Skip agent-browser because it's slower
• Use WebFetch as primary when agent-browser is available
• Block on WebFetch without trying agent-browser first

---

Deprecated Patterns

Deprecated	Use Instead	Reason
WebSearch for crate info	Task + agent or inline mode	Structured data
Direct WebFetch	actionbook + agent-browser	Pre-computed selectors
Guessing version numbers	Always fetch from source	Prevents misinformation

Error Handling

Error	Cause	Solution
Agent file not found	Skills-only install	Use inline mode
actionbook unavailable	MCP not configured	Fall back to WebFetch
agent-browser not found	CLI not installed	Fall back to WebFetch
Agent timeout	Site slow/down	Retry or inform user
Empty results	Selector mismatch	Report and use WebFetch fallback

Proactive Triggering

This skill triggers AUTOMATICALLY when:

• Any Rust crate name mentioned (tokio, serde, axum, sqlx, etc.)
• Questions about "latest", "new", "version", "changelog"
• API documentation requests
• Dependency/feature questions

DO NOT use WebSearch for Rust crate info. Use agents or inline mode instead.