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

With no annotations, the description carries the burden and does so well: it discloses scene-selection behavior (clearest scene by cloud share inside the requested area, not the whole tile), error semantics ('No scene: 404, not charged'), and payment requirements ('$0.009 USDC (Base or Solana) via x402'), plus the exact output fields. It omits rate limits and whether returned PNG URLs expire, which is the only material gap.

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?

Compact and front-loaded with a Use-when clause followed by Input/Output/Error/Price blocks; nearly every fragment earns its place. It is dense to the point of reading like a manual, but not padded.

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?

No output schema exists, so the description compensates by enumerating returns (JSON PNG URL, scene date, area cloud %, alternatives) and error/payment behavior. It is nearly complete; only minor edges like size default interplay with radius_m and URL lifetime are left implicit and covered by the schema instead.

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 100%, so the baseline is 3, but the description adds real value beyond the schema: it enumerates mode values (true_color, false_color, ndvi, ndwi, moisture), states the radius_m working range (200-10000), and clarifies that other mode URLs are returned alongside the chosen one. That goes beyond what the terse schema descriptions provide.

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 ('see a place from above'), names the concrete product (Sentinel-2 true color / NDVI imagery) and its scope, so it is immediately distinguishable from every sibling (crypto, KR trade, weather, etc.). An agent knows exactly what capability this unlocks.

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?

'Use when an agent must see a place from above or check vegetation, water or change' gives a clear positive trigger context. There are no realistic alternative siblings to route to, so no exclusion clause is needed, but it also gives no when-not guidance (e.g., clouds/coverage limits).

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