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

Annotations already declare readOnly/non-destructive/openWorld=false, so the safety profile is covered. The description adds meaningful behavioral context beyond that: results are scoped to 'screens in locations you can see' and calling requires the `playback-log.view` permission. It does not mention pagination or result-size behavior, keeping it just 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?

Tight and front-loaded: the core output description comes first, then the disambiguating siblings, then the permission. Every sentence earns its place 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?

An output schema exists so return format needn't be restated, and annotations cover safety. The description still supplies the scoping rule, permission prerequisite, and sibling disambiguation, making it complete for an agent to call 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%, with ISO-datetime defaults documented for to/from and the screenId restriction explained inline, so the schema carries the burden. The description's 'time window' phrasing adds only modest semantic framing over that baseline.

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 report verb and resource ('proof-of-play rollup for a time window') and enumerates its contents (plays, watch time, skips, failures per piece of content, reporting screens). The framing question 'how did the promo actually do?' further pins the intent, and it is clearly distinct from uptime and audit siblings.

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?

Explicitly routes to alternatives with the selecting condition: get_uptime_report for whether screens were online and search_audit_log for who changed content. It also states the data-scope constraint and the required permission, leaving nothing to inference.

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