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

Beyond the readOnlyHint=true annotation, it discloses that results preserve the journey graph (steps, edges, prefixes) along with truncation metadata and warnings, and clarifies that counts are journeys rather than users/sessions. That is meaningful behavioral context an agent could not infer from annotations or schema.

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 purpose and example, then the constraint notes. It is dense and slightly run-on in a single paragraph, but every sentence (example, no-compare note, graph/truncation note, prerequisite, required-fields rule) carries information.

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 an output schema present, the description needn't explain return values, yet it still summarizes that counts are journeys and that truncation metadata/warnings accompany results — enough for an agent to interpret output. The prerequisite pointer to the tracking guide covers the deep nested definition semantics.

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 already high (83%), so the baseline would be 3, but the description adds a genuinely useful constraint: every definition field except start, end and breakdown is required. That is a rule the schema technically encodes but is easy to miss across the large nested object.

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 description states a specific verb and resource ('see the journeys users or sessions take through events') and grounds it with a concrete example (page_view labelled by page, what follows a start item or leads to an end item). It is clearly distinguishable from a funnel/query tool by its start/end/breakdown framing, though it never names a sibling it replaces.

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?

It gives a prerequisite ('Read d8a_get_tracking_guide topic paths-definition first') and an explicit when-not/alternative pattern ('No compare: run it twice with different dates'). It stops short of explicitly contrasting with d8a_run_funnel, which an agent might reasonably confuse this with.

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