Vitals summary

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), so the bar is lower. The description adds real behavioral context: the 28-day window, user-weighting, and that values are flagged against Google's bad-behaviour thresholds, with the specific crash (1.09%) and ANR (0.47%) cutoffs.

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, front-loaded with the aggregate scope and followed by the measurement window and flagging rule. No filler sentences.

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 carries the return-value burden, and it does state what is returned (latest 28-day user-weighted value per vital) and the flagging criterion. It stops short of saying what a 'flag' looks like (status vs. boolean), a minor gap for a summary tool.

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?

There is one optional parameter and schema description coverage is 100%, with the schema already documenting package_name and its PLAY_MCP_PACKAGE default. The description adds nothing about parameters, so the 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 resource (all six vitals) and scope (latest 28-day user-weighted value of each). The phrase 'all six vitals at once' implicitly differentiates it from the single-vital siblings (crash_rate, anr_rate, slow_start_rate, etc.), though no sibling is named explicitly.

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 only implied: an agent can infer this is the aggregate alternative to the six single-vital tools, but the description never says when to prefer it over them or when-not to use it. No prerequisites or exclusions are given.

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