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

Annotations already cover read-only, idempotent, and non-destructive behavior, lowering the burden on the description. The description adds useful context beyond annotations: the Investor plan API key requirement, links to get the key, and the output characteristic of marking a winner on price, yield, and appreciation.

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?

The core purpose is front-loaded in the first sentence, followed by necessary auth guidance and a concrete example. The URLs add length but are operationally relevant, so the description remains efficiently structured.

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 straightforward four-parameter comparison tool with an output schema present, the description supplies purpose, result semantics, authentication requirements, and a worked example. There is no critical missing information for an agent to invoke it correctly.

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%, and each parameter already has clear descriptions with examples. The description's example reinforces the expected format but adds no substantive meaning beyond what the input schema provides, so the baseline of 3 is appropriate.

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 ('Compare'), a specific resource ('two US markets side by side'), and a distinctive behavior ('winner marked on price, yield and appreciation'). It is immediately distinguishable from siblings like get_market_health, get_market_summary, list_markets, and search_markets.

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?

The description clearly implies the use case: head-to-head comparison of exactly two markets. It does not explicitly name alternatives or exclusions, but the purpose is specific enough that an agent can infer when to use this tool over the siblings.

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