typescript

A rule requiring structured type reasoning before implementing TypeScript code or answering TypeScript questions. TypeScript is JavaScript with added checks for data types and interfaces.

In plain words
What is it for?
Use it during TypeScript development to review interfaces, generics, type constraints, and the correctness of proposed solutions.
Why use it?
It helps catch type errors, unclear generic constraints, incorrect feature usage, and edge cases before code is written or guidance is given.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/marcopesani/think-mcp-server/typescript
Clone the repo
git clone --depth 1 https://github.com/marcopesani/think-mcp-server

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 372 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00372
Opus 5 $0.00000 $0.00186
Sonnet 5 $0.00000 $0.00074
Haiku 4.5 $0.00000 $0.00037

Measured 2d ago against content hash 1d094344923f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

typescript scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/typescript.mdc · 48 lines

What it actually says

Using the think tool for TypeScript Development

Before implementing any TypeScript code or responding to technical questions, use the think tool to:

  • Analyze type definitions and interfaces that might be relevant
  • Check for potential type errors or edge cases
  • Reason through generics and type constraints
  • Verify the correct usage of TypeScript features

Here's an example of TypeScript-specific reasoning with the think tool:

<think_tool_typescript_example> User wants to implement a generic state management hook in React TypeScript

  • Analysis of requirements:

    • Need to handle any data type (generic typing)
    • Must preserve type information throughout state lifecycle
    • Should provide typesafe update methods
    • Need to consider immutability patterns
  • Type constraints to consider:

    • Should T extend object, or allow primitives?
    • Is Partial appropriate for updates?
    • Should we use Record<string, unknown> as fallback?
  • Implementation considerations:

    • useState as foundation
    • Add typed setter methods that preserve generics
    • Consider callback pattern for atomic updates
    • Check for compatibility with React's rules of hooks
  • Approach:

  1. Define generic interface for the hook's return value
  2. Implement useState with proper generic typing
  3. Create typed update methods that maintain type safety
  4. Add JSDoc comments for better developer experience
  5. Return immutable state with properly typed methods </think_tool_typescript_example>

When helping with TypeScript challenges:

  1. First analyze the type system implications
  2. Consider TypeScript-specific edge cases
  3. Reason through type narrowing and widening
  4. Check for compatibility with the TypeScript compiler version
  5. Consider type inference and explicit type annotations
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 48 lines · 372 tokens per session scan A 1d094344923f

Subscribe to this mod's changes

typescript is a cursor rule published in the GitHub repository marcopesani/think-mcp-server (24 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 372 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.