Scripting

mcp automatically switches to JSON output when piped or redirected, making it easy to use in shell scripts, CI/CD pipelines, and automation. You can also force JSON with --json.

Basics

Output format detection

When piped (non-interactive), mcp outputs JSON by default. In interactive terminals, it shows human-readable tables. Use --json to force JSON in any context:

# These all produce JSON:
mcp sentry search_issues '{"query": "..."}' | jq '.'   # piped → JSON
mcp sentry --list > tools.json                           # redirected → JSON
mcp sentry --list --json                                 # explicit → JSON

Output goes to stdout

All tool results are JSON on stdout:

result=$(mcp sentry search_issues '{"query": "is:unresolved"}')
echo "$result" | jq '.content[0].text'

Errors go to stderr

Errors and status messages go to stderr, so they don't pollute your data:

# This captures only the JSON, not auth messages or warnings
mcp sentry search_issues '{"query": "is:unresolved"}' > results.json

Exit codes

• 0 — Success

• 1 — Error (connection failed, tool error, bad config, etc.)

if mcp sentry --list > /dev/null 2>&1; then
    echo "Sentry is configured and reachable"
else
    echo "Sentry is not available"
fi

Piping input

When no JSON argument is provided on the command line, mcp reads from stdin (if it's not a terminal):

# From a file
cat query.json | mcp sentry search_issues

# From another command
jq -n '{"query": "is:unresolved"}' | mcp sentry search_issues

# Here document
mcp sentry search_issues <<'EOF'
{"query": "is:unresolved", "sort": "date"}
EOF

If stdin is a terminal (interactive), mcp uses {} as the default argument. This is why mcp sentry --list works without any input.

Parsing with jq

Get tool names

mcp sentry --list | jq -r '.[].name'

Extract text content

mcp sentry search_issues '{"query": "is:unresolved"}' \
  | jq -r '.content[] | select(.type == "text") | .text'

Check for errors

result=$(mcp sentry search_issues '{"query": "bad query"}')
is_error=$(echo "$result" | jq -r '.isError // false')
if [ "$is_error" = "true" ]; then
    echo "Tool returned an error"
fi

Common patterns

Loop over results

# Get all tool names and call each one with empty args
mcp sentry --list | jq -r '.[].name' | while read tool; do
    echo "=== $tool ==="
    mcp sentry "$tool" 2>/dev/null || echo "(failed)"
done

Build arguments dynamically

project="my-project"
query="is:unresolved level:error"
args=$(jq -n --arg q "$query" --arg p "$project" \
    '{"query": $q, "project": $p}')
mcp sentry search_issues "$args"

Chain multiple servers

# Get Sentry errors, format them, post to Slack
errors=$(mcp sentry search_issues '{"query": "is:unresolved level:error"}' \
    | jq -r '.content[0].text')

message="Unresolved errors from Sentry:\n${errors}"
mcp slack send_message "$(jq -n --arg text "$message" \
    '{"channel": "#alerts", "text": $text}')"

Cron job

#!/bin/bash
# /etc/cron.d/check-errors — run every hour

export SENTRY_TOKEN="your-token"
export MCP_CONFIG_PATH="/opt/mcp/servers.json"

count=$(mcp sentry search_issues '{"query": "is:unresolved level:error"}' \
    | jq '.content[0].text | length')

if [ "$count" -gt 0 ]; then
    echo "Found $count unresolved errors" | mail -s "Sentry Alert" [email protected]
fi

CI/CD

GitHub Actions

- name: Check for critical Sentry issues
  env:
    MCP_CONFIG_PATH: ./ci/mcp-servers.json
    SENTRY_TOKEN: ${{ secrets.SENTRY_TOKEN }}
  run: |
    result=$(mcp sentry search_issues '{"query": "is:unresolved level:fatal"}')
    count=$(echo "$result" | jq '.content | length')
    if [ "$count" -gt 0 ]; then
      echo "::warning::Found unresolved fatal issues in Sentry"
    fi

Tips

• Always quote JSON arguments — Shell metacharacters in JSON can cause issues

• Use jq -n — When building JSON arguments with variables, jq -n is safer than string interpolation

• Redirect stderr — Use 2>/dev/null to suppress auth messages in scripts

• Set MCP_TIMEOUT — Increase for slow servers: MCP_TIMEOUT=120 mcp slack --list

• Non-interactive stdin — When piping or in cron, stdin is not a terminal, so mcp reads from it. Pass {} explicitly if the tool needs no arguments: echo '{}' | mcp server tool