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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive), so the bar is lower. The description still adds genuinely new behavior: the call is free, and the response includes a recent-run-free determination. That is cost and result semantics the agent could not derive from annotations alone.

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 tight sentences with the core value (price, free-status) front-loaded and the endpoint note parenthetical. The '[read-only]' tag mildly duplicates the readOnlyHint annotation, but nothing else is wasted.

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 carries the burden of describing return values, and it does: a price quote plus a free-run determination. For a two-parameter read-only wrapper this is close to complete, with only the ambiguous owner-check instruction as a gap.

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%, with both brandId (including the 'personal' value and default) and snapshotId documented inline. The description adds no new detail about either parameter, so the schema does the heavy lifting and 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?

Names a specific verb and resource: it returns the Embers price of a deep dive on a saved snapshot plus whether a recent run makes it free. That is enough to separate it from the run/get siblings. It stops short of naming ads_deep_dive_run explicitly, so the contrast is inferred from 'Charges nothing.'

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?

'Ask the owner before running' and 'Charges nothing' imply this is the pre-flight check before spending, which is useful context. But the phrasing is ambiguous about whether the owner check applies to this tool or to the subsequent run, and no alternative is named as a substitute. Usage is implied rather than stated.

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