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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint=false), so the bar is lower, and the description adds genuinely new behavior: output resolution adapts to the range (hours for two days or less, then days/weeks/months). That is information an agent cannot get from annotations or the schema. It omits any statement about truncation or result limits, so it stops short of a 5.

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 resource and followed immediately by the resolution rule; nothing is padded. It is compressed to the point of being slightly cryptic about what the buckets contain, but there is no wasted wording.

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?

For a read-only tool whose safety is fully declared by annotations and whose five parameters are fully documented in the schema, the main remaining gaps are which question this tool answers versus its siblings and what the time series values represent. The granularity rule covers part of the return shape in the absence of an output schema, but the definition is thin overall.

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% – from/to, mode, metric and project_id all carry their own defaults and enumerated values in the schema. The description's range note loosely relates to from/to but adds no syntax, format, or interaction detail beyond what the schema already provides, 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?

The description states a specific resource and shape of result: a single metric sampled over time. It does not name or contrast any sibling (get_breakdown, get_summary, get_funnel), so the agent must infer that this is the temporal-series variant. Clear purpose, but no explicit sibling differentiation.

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?

There is no explicit when-to-use guidance and no routing to alternatives among get_breakdown, get_failure_breakdown, get_funnel or get_summary. The granularity note implies that short ranges are handled in hours, which hints at appropriate usage, but the agent is left to infer which tool answers which question.

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