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delimit_heartbeat_check

Walks the heartbeat directory and classifies each service as ok, stale, failed, or never seen to surface silent daemon staleness before customer impact.

Instructions

Walk the heartbeat directory and report which scheduled services are stale (LED-1412).

When to use: as part of the session-start ritual to surface silent daemon staleness before it becomes a customer-visible incident. The 2026-05-15 incident — delimit-reddit-proxy.service inactive for 13 days, all reddit scans 429-failing silently, founder noticing only via "3 day old posts" — is the failure mode this prevents. Each scheduled task writes ~/.delimit/heartbeats/<service>.json after every run; this tool walks the dir and classifies each service. When NOT to use: for one-off liveness checks (just read the file yourself) or for full-host metrics (delimit_obs_status). Phase 2 will add an external deadman ping for full-host outages — heartbeats here are local-only.

Sibling contrast: delimit_obs_status reports composed runtime observability metrics; this reports per-service liveness based on last_run timestamps written by each daemon. delimit_gov_health reports the kernel layer.

Side effects: read-only on the heartbeat directory. No network, no write, no ledger, no notification.

Classification (most-severe-first):

  • parse_error: heartbeat file unreadable

  • failed: status='failed' in the record

  • stale: last_run older than service-specific threshold

  • degraded: status='degraded' in the record

  • never_seen: configured service has no heartbeat file yet

  • unknown_age: heartbeat exists but timestamp won't parse

  • ok: status='ok' AND last_run within threshold

Per-service thresholds default to sensible values (reddit/social-loop 2h, inbox 30min, daily timers 36h). Override via <dir>/_thresholds.json — JSON map of {service_name: seconds}.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
heartbeat_dirNoOverride the heartbeat directory. Default: $DELIMIT_HEARTBEAT_DIR env var or ~/.delimit/heartbeats/.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Discloses side effects ('read-only on the heartbeat directory. No network, no write, no ledger, no notification') and lists classification categories (parse_error, failed, stale, etc.). No annotations provided, but description fully covers behavioral traits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Well-structured with front-loaded purpose, clear sections for usage, side effects, and classification. Though verbose, it is efficiently organized and each section adds value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Complete given single parameter and presence of output schema. Covers all relevant aspects: input, behavior, classifications, thresholds, override mechanism, and future plans.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% (one parameter with description). The description adds context about default directory lookup (env var, fallback path) that enriches the schema's description, earning above baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Walk the heartbeat directory and report which scheduled services are stale', specifying the verb (walk/report) and resource (heartbeat directory). It distinguishes from siblings like delimit_obs_status and delimit_gov_health by contrasting the scope of liveness vs observability vs system health.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly specifies when to use ('as part of the session-start ritual') and when not to use ('for one-off liveness checks' or 'full-host metrics'), naming alternative tools. Also mentions future phase for external deadman ping.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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