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

readOnlyHint=true already establishes it is a safe read, so the description's job is lighter. It adds real behavioral context beyond the annotations: the four problem categories it aggregates, the 'since when' detail on downtime, and that it is derived from GET /api/checks. It does not describe result shape or pagination, but for an aggregate reader that is a minor omission.

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?

A single dense sentence, front-loaded with the 'One-call health overview' hook, followed by the enumerated problem categories. Every clause earns its place and nothing is padded.

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?

No output schema exists, so the description must convey the returned content, and it effectively enumerates the problem categories an agent will receive. Combined with only two optional, fully-documented params and a readOnly annotation, this is nearly complete; it only lacks return-format specifics.

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?

Schema coverage is 100%, so both parameters (ssl_days, domain_days) including their defaults and bounds are already documented in the schema. The description mentions 'expire within N days' conceptually but adds no syntax, units, or default details beyond what the schema provides. Baseline 3 applies when the schema carries the parameter burden.

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?

States a specific verb and resource (health overview across every check) and enumerates exactly what it surfaces: DOWN checks with since-when/error, invalid SSL, certificate/domain expiry, paused/muted checks. This clearly differentiates it from siblings like updown_list_checks or updown_get_check, which return raw check data rather than a problem-focused summary.

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 'one-call health overview' framing implies when to reach for this aggregate rather than iterating per-check tools. However, it never names an explicit alternative (e.g. list_checks) or states a when-not condition, so the routing guidance is clear but not fully spelled out.

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