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

Annotations already declare the safe read-only profile, so the description is free to add value — and it does: it discloses the Exploration schema constraint, that pagePath is mapped to unifiedPagePathScreen, and that eventName should be used to match events. These are non-obvious behavioral caveats not captured in structured fields.

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?

Front-loaded with the core action and keeps the caveats in a compact NOTE clause; every sentence carries usable information. Slightly dense but not padded.

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?

No output schema exists, so the description needn't cover return values, and annotations handle safety. For a moderate 5-param read tool it covers the distinctive funnel semantics well, though date-range and property parameters remain unaddressed.

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 only 20%, so the description must compensate. It does well for funnelSteps (spelling out the simple {name, dimension, matchValue} shape) and for funnel overriding funnelSteps, but startDate, endDate, and property are left unexplained in both schema and description.

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+resource ('Run a GA4 funnel report') and pins the API version (Data API v1alpha). It distinguishes itself from the sibling run_report by noting the funnel-specific Exploration schema, so an agent can tell the two apart without opening a schema.

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?

Explains the two ways to supply funnel structure (ordered funnelSteps vs raw funnel object) and warns that pagePath is invalid here, but never states the condition under which an agent should choose this tool over run_report or run_gaql_report. Usage context is implied rather than explicit.

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