Store category rank

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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower. The description earns credit by disclosing a concrete failure behavior — an unknown app id returns 422 'App not found.' here, unlike sensortower_app_metadata — which an agent cannot derive from the schema or annotations. It omits request-cost/pagination context, but the mode requirements and error semantics add real value.

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?

Three tight sentences, each carrying distinct information: mode=current behavior, mode=history requirements plus a pointer for valid values, and the 422-versus-sibling distinction. The mode branches are front-loaded and there is no redundant restatement of the title or schema fields.

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 12-parameter, no-output-schema tool, the description covers the mode logic, the history prerequisites, and an error edge case. Remaining fields (os, limit, fields, format, dates, countries) are documented in the schema, so their absence from the description is acceptable. A brief note on what a rank row contains would fully close the gap.

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 75%, so the schema already documents most fields. The description nonetheless adds conditional semantics that the schema does not express: category and chart_type_ids are required only for mode=history, and mode=current operates on a single app id. That conditional relationship is the key semantic an agent needs and it is stated explicitly.

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+resource (returns category rank for an app) and cleanly splits it into two named modes with a precise definition of each ('every category rank an app holds right now' vs 'the daily rank series for a specific category and chart type'). This is distinguishable from siblings like sensortower_top_charts, which aggregate across apps rather than reporting a given app's rank.

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 clear mode-selection guidance: mode=current for one app id, mode=history requires category + chart_type_ids and directs the agent to sensortower_reference for valid values. It also flags a behavioral difference against sensortower_app_metadata. It stops short of stating when NOT to use this tool (e.g. preferring top_charts for aggregate rankings), so it is clear guidance without explicit exclusions.

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