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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds genuinely new behavioral context: default sort order (newest first), that each result carries monitor identity, status, trigger, timing and error/warning, and the cursor semantics for walking backwards in time. It does not mention rate limits or result-size ceilings, but for a read-only listing tool the disclosure is above average.

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?

Two dense, front-loaded sentences: the first establishes purpose, ordering and filter scope, the second covers result contents and the pagination escape hatch. Nothing is repeated from the schema or annotations and there is no filler.

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 correctly takes on the burden of describing what each run contains and how to page through older results. Combined with the fully documented input schema and read-only annotations, an agent has everything needed to call the tool correctly.

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 the baseline is 3. The description goes beyond it by summarising the filter family ('one site, one monitor or one status') and, crucially, explaining that `before` is the startedAt of the last run already retrieved — operational meaning the schema's 'the next page' phrasing only hints at.

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 ('Recent runs, newest first') plus the exact filter scope (site, monitor, status), and explicitly contrasts itself with the sibling get_run ('get_run has the detail'). An agent can distinguish it from list_checks, list_sites and get_run without opening any schema.

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?

Gives clear context for when to use it — browsing recent runs, optionally narrowed by one site/monitor/status — and names get_run as the alternative for detail. It also explains the pagination workflow ('For older runs pass `before`'). It stops short of stating exclusions (e.g. when a different listing tool is preferable) but the routing guidance is solid.

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