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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the aggregation window (28 days) and the shape of what comes back (tier, momentum). It stops short of describing pagination or result-size behavior for a 6-parameter list tool, so not a 5.

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?

Two sentences, zero waste, with the primary usage trigger front-loaded and the negative routing compressed into a single clause. Every sentence earns its place.

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?

For a read-only, 6-parameter list tool with no output schema, the description covers purpose, routing, and a hint of return shape, but leaves pagination (limit/cursor) and the chart-vs-store relationship unexplained. Adequate to select the tool, insufficient to invoke it confidently at scale.

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 33%, so the description must carry the load, and it does not. Only 'store' is obliquely implied ('in a store'); limit, cursor, context, and response_format are documented in neither the schema nor the description, and the description never explains that 'chart' must be discovered via stores_get.

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?

Names the concrete resource (OpenApps Rank), its exact semantics (a 28-day aggregate of popularity charts, with tier and momentum), and the user question it answers. An agent can distinguish it from every sibling 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?

Explicitly states the selecting condition (user asks which apps are popular in a store over the last month) and names two exclusions with their tools: charts_get for a single day's chart order, leaderboards_get for published counts. Nothing is left to inference.

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