market_charts

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

Goes well past the annotations (which only establish readOnly/idempotent/non-destructive) by disclosing the snapshot nature ('as we last measured it'), exact pricing (10 credits for the list, 50 more per row with estimates), and the platform limit with the reason ('no public top chart, and a number there would be invented'). This is exactly the kind of cost and staleness context an agent needs.

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 dense sentences, front-loaded with what is returned, then cost, then the platform caveat. Every clause carries information; nothing is padding.

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 burden of describing the return shape and does so ('ranked app ids ... with the day it was read', plus monthly values and entry thresholds at #10/#50/#100). Cost, platform scope and optional estimate expansion are all covered, so nothing needed to call it correctly is missing.

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 100%, so the baseline is 3. The description earns above that by mapping kind values to what estimates actually mean ('revenue on Top Grossing, downloads on Top Free') and by naming genre as the optional category, adding interpretation the terse schema strings do not.

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+resource: 'the ranked app ids for a storefront, list kind and optional category, with the day it was read.' The phrase 'One top chart as we last measured it' implicitly separates it from the bulk-chart sibling get_charts, but no sibling is ever named, so differentiation is left to inference.

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 through the credit cost and the platform constraint ('App Store only'), and there is an exclusion for Google Play. However, it never says when to prefer this over get_charts, get_chart_movers, market_movers or market_new_apps, or what to use instead for Google Play, so the agent must infer routing.

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