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

Annotations already declare readOnlyHint=true, destructiveHint=false and a closed-world scope, covering the safety profile. The description adds return-shape context (traits, sessions, pageviews, first source), but says nothing about pagination behavior, total counts, or ordering. Some added value over annotations, but not rich.

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?

A single dense sentence that front-loads the resource and scope. Every clause earns its place by describing returned content; nothing is padded, though the trailing list of returned fields makes it slightly run-on.

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 usefully sketches the return shape (identified vs anonymous, sessions, pageviews, first source), and schema coverage is high for the 10 parameters. Only minor gaps remain, such as pagination and result ordering.

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 90%, so the schema already documents nearly every parameter, including date, kind, limit, period and filter syntax. The description's 'identified users (with traits)' loosely maps to the kind enum but adds no syntax or format 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?

States a specific verb (list) and resource (users) and adds scope: 'active in the period'. It even enumerates the returned entities (identified users with traits, anonymous visitors with sessions/pageviews/first source), which cleanly separates it from the singular get_user. It does not name a sibling explicitly, so it falls just short of a 5.

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?

Usage is implied by 'active in the period' plus the kind enum (all/identified/anonymous), but there is no explicit when-to-use vs get_user/list_sessions guidance and no stated exclusions. Adequate context without routing help.

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