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

It goes well beyond the readOnly/idempotent/destructive annotations: it discloses that no e-mail is sent, no outbound call is made, that the ingest only records `alert_pending`, that the cron converts this within 5 minutes with reason "fail", and that alerts are capped at one per 24 hours (or alert_repeat_sec). That is exactly the kind of side-effect and timing information an agent cannot get from structured fields.

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

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

The purpose is front-loaded and the paragraph is reasonably tight, but 'Failing is not proof of life either: the clock keeps running' is documentation prose that does not help an agent select or invoke the tool and slightly dilutes the signal.

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

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

With no output schema, the description compensates by describing what happens after the call (alert_pending recorded, alert produced within 5 minutes) and how repeats are throttled. For a one-parameter signal tool this is nearly complete, though it omits what the immediate call response looks like.

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

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

There is a single required parameter and schema description coverage is 100% (the schema already says it is the Monitor ID from Monitor.ingest_url), so the schema carries the meaning. The description adds nothing about the `id`, which is acceptable at baseline but not above it.

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

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

The opening sentence 'Record a failed run' gives a concrete verb plus the signal type, which an agent can map onto the monitoring domain and separate from signal_start/signal_slug by the 'fail' semantics. It stops short of explicitly contrasting itself with those sibling signal tools, so it is clear but not fully differentiated.

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

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

The description explains the downstream timing (alert dispatched on the next five-minute check) and the repeat cap, which implies when a fail signal is meaningful, but it never states when to choose this over signal_start, signal_exit_code, or signal_slug, nor any prerequisites. Usage is implied rather than guided.

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