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

Annotations already declare readOnlyHint=true, so safety is covered, and the description adds real context beyond them: the fetch is keyed by token and the results flag "can be large," warning about payload size. It still says nothing about error behavior for invalid tokens or pagination.

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?

One dense sentence plus a short endpoint reference; the core action and the optional enrichments are front-loaded with 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 signals what the response can contain (metrics for the last hour, last 5 request results) and flags size risk, which is the right level of detail for a read-only getter. It stops short of noting failure modes for a bad token.

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 description coverage is 100%, so all three parameters are already documented with equal or greater detail (including the token source example and the size warning). The description largely restates the schema, so the baseline 3 applies.

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?

Specific verb + resource: "Fetch a single check by token," with the endpoint cited. It is distinguishable from updown_list_checks, but it does not explicitly separate itself from the sibling updown_get_check_metrics, which it partially overlaps by offering optional metrics.

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?

Usage is only implied through the optional metrics/results flags; there is no explicit when-to-use statement, no exclusion, and no pointer to the metrics-specific sibling that an agent would need to choose correctly between the two.

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