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

Annotations cover the safety profile (readOnly, non-destructive, openWorld), and the description adds substantial context they cannot: the exact return contents (side-by-side JPEG with date labels, changed-pixel share, brightness change, cloud/haze/snow estimate per date, plain-language verdict), the pricing model ($0.013 USDC via x402, accepted chains), and a free sample input. This is unusually rich behavioral disclosure.

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 paragraph, but front-loaded with purpose and outputs before parameters and pricing. The example input is long yet earns its place by demonstrating a free call, so there is little wasted text.

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 10-parameter tool with no output schema and zero required params, the description covers outputs, defaults, location-mode alternatives, and payment mechanics. An agent has everything needed to construct a valid call without opening the schema.

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?

With only 50% schema coverage, the description compensates by restating the three location modes (place OR lat+lon+radius_km OR bbox), the radius and width ranges with defaults, and the defaulting relationships (date_before defaults one year before date_after; date_after defaults yesterday). It stops short of explaining the layer enum options, but the schema carries those.

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: before/after comparison of the same area on two dates using NASA GIBS true-color imagery, naming the sources (MODIS/VIIRS, ~250 m). This clearly distinguishes it from the sibling satellite_image (single image) and tells an agent exactly what artifact it produces.

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?

Gives concrete when-to-use domains (floods, wildfires and burn scars, drought and lake levels, snow cover, deforestation, construction at regional scale). It does not explicitly name satellite_image as the alternative for single-date imagery, but the use-case framing is strong enough to route correctly.

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