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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description does add real value beyond them by disclosing the sampling behavior and the auth/scope constraint ('Anonymous preview is limited to agentanalytics-demo synthetic read-only data; sign in for your own projects'), which tells the agent when results will be demo data rather than real data. It still says nothing about pagination, limits, or the shape of the returned keys.

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?

It is short, but the two ideas are run together without punctuation ('...recent events Anonymous preview is limited to...'), which hurts readability and makes the disclaimer read as part of the functional clause. The functional statement is front-loaded, which is the right ordering.

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 is the only place that can explain the return shape (keys grouped per event name) and it does not. It also omits any differentiation from the sibling 'properties', leaving an agent unable to choose between the two from the definition alone.

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 'since', 'sample' and 'project' are already fully documented in the schema. The phrase 'sampled from recent events' loosely echoes the 'sample' and 'since' parameters but adds no syntax, default, or interaction detail beyond the schema. 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 fragment 'Property keys by event name, sampled from recent events' communicates the resource returned but supplies no verb and no scope, so it is closer to a label than a stated purpose. A sibling tool literally named 'properties' exists, and nothing here distinguishes the two, which is exactly the differentiation the description should have provided.

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 when-to-use guidance at all: no condition, no prerequisite, and no mention of the closely named sibling 'properties' or any alternative such as 'query' or 'analytics_breakdown'. The agent must infer usage entirely from the name.

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