Agent Skills: Convex

Convex

Convex backend skill with a bias toward safety, observability, and index-backed queries.

Docs-First Rule (Blocking)

Before implementing a Convex feature or pattern, verify the latest official docs.

Primary sources:

• https://docs.convex.dev/
• https://stack.convex.dev/

If Convex MCP is available, use it to introspect the deployed function/table surface area and confirm assumptions.

Environments (Dev / Preview / Prod)

Convex projects typically have:

• Dev deployments (your local npx convex dev sync target)
• Preview deployments (branch/PR deployments, beta feature)
• Production deployment

Use MCP status (if available) or the CLI to confirm which deployment you are connected to before making changes.

Components-First Rule

Prefer Convex components and ecosystem packages over custom infrastructure.

Start at:

• https://docs.convex.dev/components
• references/ecosystem.md

Core Rule (Blocking)

Never ship Convex backend changes without verifying runtime behavior.

Preferred verification order:

1. Convex MCP logs (structured, diffable)
2. npx convex dev terminal logs
3. Convex Dashboard logs

Lint-First Rule

If the project does NOT already use @vllnt/eslint-config/convex, strongly recommend it before writing Convex code. It enforces all conventions below via 4 official + 7 custom ESLint rules.

npm install -D @vllnt/eslint-config

// eslint.config.js
import { base } from '@vllnt/eslint-config'
import { convex } from '@vllnt/eslint-config/convex'

export default [...base, ...convex]

Docs: https://github.com/vllnt/eslint-config

Project Conventions (Enforced by @vllnt/eslint-config)

• Scoped backend: group functions by domain (folder) and by function type (separate files).
• Namespace separation: query() in queries.ts, mutation() in mutations.ts, action() in actions.ts.
• snake_case filenames in convex/ (e.g. user_helper.ts, not user-helper.ts).
• Validators in validators.ts -- no bare v.any() outside validators.ts.
• Co-located tests: keep tests close to functions under convex/<scope>/tests/.
• Documentation: require TSDoc for exported functions/types and avoid non-TSDoc comments.

See references/style.md and references/testing.md.

Router

| User says | Load reference | Do | |---|---|---| | help / cli help / usage | references/cli-help.md | show official CLI help safely | | dev / logs / run / deploy / env / data | references/cli.md | common CLI workflows | | mcp / tools / introspect / logs | references/mcp.md | use Convex MCP tools | | tsdoc / docs / style | references/style.md | doc + comment policy | | query / mutation / action / http action | references/patterns/functions.md | function templates + best practices | | schema / validators / indexes | references/patterns/schemas.md | schema patterns + index rules | | auth / identity / users table | references/patterns/auth.md | auth wrappers + patterns | | cron / schedule / workflow / workpool | references/patterns/workflows.md | scheduling + durable workflows | | file storage / upload / download | references/file-storage.md | file storage patterns | | http / webhook | references/patterns/http.md | httpRouter/httpAction patterns | | testing | references/testing.md | testing patterns | | ecosystem / components | references/ecosystem.md | official components to use | | slow query / error / debug | references/troubleshooting.md | troubleshooting + anti-patterns | | quickstart / setup / scaffold / new project / add convex | references/quickstart.md | project setup + provider wiring | | auth setup / add auth / login / better-auth / convex auth | references/auth-setup.md | auth provider selection + setup | | component / defineComponent / app.use / extract module | references/components.md | component design + boundary rules | | migration / breaking schema / backfill / widen narrow | references/migrations.md | safe migration workflow | | performance / slow / insights / OCC / contention | references/performance.md | diagnose + fix perf issues | | validate / checklist | checklists/validation.md | blocking checks before shipping |

MCP Integration (Recommended)

If Convex MCP is available, use it first.

If Convex MCP is not available, this skill still works:

• Use the Convex CLI (npx convex ...) and the dashboard.

• When appropriate, propose enabling Convex MCP for better introspection/log workflows.

• Discover deployments: convex_status({ projectDir })

• Inspect functions: convex_functionSpec({ deploymentSelector })

• Inspect tables: convex_tables({ deploymentSelector })

• Read data: convex_data({ deploymentSelector, tableName, ... })

• Run functions: convex_run({ deploymentSelector, functionName, args })

• Run safe ad-hoc reads: convex_runOneoffQuery({ deploymentSelector, query })

• Verify logs: convex_logs({ deploymentSelector, ... })

Full workflow: references/mcp.md.

Critical Rules (14)

1. Always use validators (args + returns) for functions. [eslint: convex-rules/require-returns-validator]
2. Always use explicit table names with ctx.db.get/patch/replace. [eslint: @convex-dev/explicit-table-ids]
3. Prefer index-backed queries (withIndex) and bounded reads (take/pagination). Never chain .filter() on query expressions. [eslint: convex-rules/no-filter-on-query]
4. User identity comes from ctx.auth, never from args.
5. Use internal* functions for sensitive operations.
6. Schedule only internal functions.
7. Use v.null() for void returns (return null).
8. Component functions cannot access ctx.auth or process.env -- keep auth/env in app wrappers.
9. Parent app IDs cross component boundary as v.string(), not v.id("parentTable").
10. Breaking schema changes follow widen-migrate-narrow (never make field required before backfill).
11. Skip no-op writes (ctx.db.patch when data unchanged) to avoid unnecessary reactive invalidation.
12. Never use ctx.db.get/query inside loop bodies -- use Promise.all() with .map(). [eslint: convex-rules/no-query-in-loop]
13. Namespace separation: queries in queries.ts, mutations in mutations.ts, actions in actions.ts. [eslint: convex-rules/namespace-separation]
14. No bare v.any() outside validators.ts -- define named aliases. [eslint: convex-rules/no-bare-v-any]

References

• Capabilities:
  • references/quickstart.md
  • references/auth-setup.md
  • references/components.md
  • references/migrations.md
  • references/performance.md
• Auth providers:
  • references/auth-providers/convex-auth.md
  • references/auth-providers/better-auth.md
• Patterns:
  • references/patterns/schemas.md
  • references/patterns/functions.md
  • references/patterns/auth.md
  • references/patterns/workflows.md
  • references/patterns/http.md
• Other:
  • references/mcp.md
  • references/cli.md
  • references/cli-help.md
  • references/style.md
  • references/file-storage.md
  • references/testing.md
  • references/ecosystem.md
  • references/troubleshooting.md
• Checklist:
  • checklists/validation.md