Writing queries, mutations, actions, and HTTP actions with proper argument validation, error handling, internal functions, and runtime considerations

Convex Functions Master Convex functions including queries, mutations, actions, and HTTP endpoints with proper validation, error handling, and runtime considerations. Code Quality All examples in this skill comply with @convex dev/eslint plugin rules: Object syntax with handler property Argument validators on all functions Explicit table names in database operations See the Code Quality section in [convex best practices](../convex best practices/SKILL.md) for linting setup. Documentation Sources Before implementing, do not assume; fetch the latest documentation: Primary: https://docs.convex.dev/functions Query Functions: https://docs.convex.dev/functions/query functions Mutation Functions: https://docs.convex.dev/functions/mutation functions Actions: https://docs.convex.dev/functions/actions HTTP Actions: https://docs.convex.dev/functions/http actions For broader context: https://docs.convex.dev/llms.txt Instructions Function Types Overview Type Database Access External APIs Caching Use Case Query Read only No Yes, reactive Fetching data Mutation Read/Write No No Modifying data Action Via runQuery/runMutation Yes No External integrations HTTP Action Via runQuery/runMutation Yes No Webhooks, APIs Queries Queries are reactive, cached, and read only: Mutations Mutations modify the database and are transactional: Actions Actions can call external APIs but have no direct database access: HTTP Actions HTTP actions handle webhooks and external requests: Internal Functions Use internal functions for sensitive operations: Scheduling Functions Schedule functions to run later: Examples Complete Function File Best Practices Never run npx convex deploy unless explicitly instructed Never run any git commands unless explicitly instructed Always define args and returns validators Use queries for read operations (they are cached and reactive) Use mutations for write operations (they are transactional) Use actions only when calling external APIs Use internal functions for sensitive operations Add "use node"; at the top of action files using Node.js APIs Handle errors with ConvexError for user facing messages Common Pitfalls 1. Using actions for database operations Use queries/mutations instead 2. Calling external APIs from queries/mutations Use actions 3. Forgetting to add "use node" Required for Node.js APIs in actions 4. Missing return validators Always specify returns 5. Not using internal functions for sensitive logic Protect with internalMutation References Convex Documentation: https://docs.convex.dev/ Convex LLMs.txt: https://docs.convex.dev/llms.txt Functions Overview: https://docs.convex.dev/functions Query Functions: https://docs.convex.dev/functions/query functions Mutation Functions: https://docs.convex.dev/functions/mutation functions Actions: https://docs.convex.dev/functions/actions

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