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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real value with the 'No cross-org access' authorization constraint and the underlying endpoint. It does not explain the 'recent snapshot headers' mode — how many are returned, ordering, or pagination — which is the main behavioral unknown.

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 read-only marker and the primary behavior front-loaded, followed by the access constraint and endpoint provenance. The '[read-only]' tag merely restates readOnlyHint, but the rest earns its space.

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 explaining what comes back, and 'snapshot headers' is left undefined — an agent cannot tell what fields or shape to expect, nor how many headers the no-id mode returns. For a dual-mode read tool this is a meaningful but not fatal gap, since the input side is largely covered.

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 50%: brandId is fully documented in the schema, while id has no schema description at all. The description partially compensates by framing id as the identifier of a saved snapshot and reinforcing the active-brand default and org boundary for brandId, but it adds no format or example detail for id.

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 ('Read one saved ads data snapshot') and explicitly covers both operating modes: by id, or recent snapshot headers for the active brand. An agent can distinguish this from the mutating sibling ads_snapshot_collect, though the description never names that sibling to sharpen the contrast.

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 two modes imply when to pass an id versus when to omit it, which is useful implied guidance. However, there is no explicit statement of when to prefer this over ads_snapshot_collect (to create a snapshot) or ads_insights (to query data), and no exclusions are given.

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