bpp-connect-local-db

name: bpp-connect-local-db description: Use when user wants the agent to be able to query the local database of a .NET project — phrases like "connect to local db", "look at the db", "check the schema", "what tables exist", or any question that needs DB context. Discovers `appsettings.local.json` under cwd, parses `ConnectionStrings.DefaultConnection`, verifies the connection. Agent then explores the schema on demand via `psql`.

Overview

Project-independent helper for .NET repos: locates appsettings.local.json under cwd, parses the connection string, and verifies the agent can reach the local PostgreSQL DB. After connecting, the agent should familiarize itself with the schema on demand by issuing targeted psql queries — not by pre-dumping everything.

When to Use

User asks anything that needs DB context: schema questions, table/column lookups, enum values, FK relationships
"connect to local db", "check the schema", "what tables exist", "show columns of X"
Connection is PostgreSQL via appsettings.local.json

Don't use for:

Non-Postgres DBs — fail loudly, don't improvise
Production / remote DBs
Any write or modify operation (read-only)

Steps

1. Find `appsettings.local.json` under cwd

find . -name 'appsettings.local.json' \
  -not -path '*/bin/*' -not -path '*/obj/*' \
  -not -path '*/node_modules/*' -not -path '*/.git/*'

0 matches → tell user "no appsettings.local.json under cwd"; stop.
1 match → use it.
≥2 matches → list them, ask the user which to use. Never silently pick.

2. Extract `DefaultConnection`

jq -r '.ConnectionStrings.DefaultConnection' <path>

If null / missing → tell user; stop.

3. Validate Postgres + parse

.NET format: Host=H;Port=P;Database=D;Username=U;Password=PW (semicolon-separated, case-insensitive keys).

If the string contains Server= or Data Source= (SQL Server) or Server=...;Uid= (MySQL) → tell user only PostgreSQL is supported; stop.

Required keys: Host, Port, Database, Username, Password.

4. Verify connection

PGPASSWORD=<pw> psql -h <h> -p <p> -U <u> -d <db> -tAc "SELECT version();"

If the query succeeds, report a one-line confirmation: connected to <db>@<host>:<port> (server <version>). Don't dump the schema.

5. Explore the schema on demand

After connection is verified, the agent should familiarize itself with the schema only as needed to answer the user's actual request. Use targeted queries from the table below — never pre-dump the full DDL.

Schema Exploration Quick Reference

Need	Query
List tables	`SELECT tablename FROM pg_tables WHERE schemaname='public' ORDER BY tablename;`
List enums	`SELECT typname FROM pg_type WHERE typtype='e' ORDER BY typname;`
Enum values	`SELECT unnest(enum_range(NULL::<enum_name>));`
Columns of a table	`\d <table_name>` (psql meta) or `SELECT column_name, data_type, is_nullable FROM information_schema.columns WHERE table_schema='public' AND table_name='<t>' ORDER BY ordinal_position;`
FKs of a table	`\d <table_name>` shows them inline
All FKs DB-wide	`SELECT conrelid::regclass AS tbl, conname, pg_get_constraintdef(oid) FROM pg_constraint WHERE contype='f';`
Indexes of a table	`\d <table_name>` or `SELECT indexname, indexdef FROM pg_indexes WHERE tablename='<t>';`
Search tables by name	`SELECT tablename FROM pg_tables WHERE schemaname='public' AND tablename ILIKE '%<keyword>%';`
Search columns by name	`SELECT table_name, column_name FROM information_schema.columns WHERE table_schema='public' AND column_name ILIKE '%<keyword>%';`

Run via:

PGPASSWORD=<pw> psql -h <h> -p <p> -U <u> -d <db> -c "<sql>"

Common Mistakes

Silent first-match pick when multiple appsettings.local.json exist → always prompt.
Pre-dumping the full DDL "to be safe" → don't. Query only what's needed for the current task.
Inline password on command line → use PGPASSWORD=... env prefix so it's not in shell history.
Assuming Postgres without checking — fail loudly if connection string is SQL Server / MySQL.
Issuing write/DDL statements — this skill is read-only.

Red Flags

About to pick first appsettings.local.json without asking → STOP, prompt user.
About to run pg_dump or fetch huge result sets preemptively → STOP, query targeted.
About to write/modify the DB → STOP, this skill is read-only.
Connection string isn't Postgres → STOP, tell user, don't try to adapt.

bpp-connect-local-db