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

With no annotations provided, the description carries the full burden. It discloses the source, the return content (signed COG band URLs for six bands plus metadata), and the in-memory caching behavior. It does not mention authentication, rate limits, or URL expiration, but the core behavioral traits are covered.

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?

Two concise sentences. The first sentence states the action and subject; the second lists the return value and the caching side effect. Every clause earns its place, and key information is front-loaded.

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?

Although there is no output schema, the description explicitly enumerates the six spectral bands and notes the inclusion of tile metadata, which covers return values. It also mentions the caching behavior that links to sibling tools. A small gap is the absence of failure/edge-case behavior, but for a fetch tool with well-documented parameters, this is reasonably complete.

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?

The input schema already provides 100% parameter coverage with descriptions for h3_cell, days_back, timestamp, and max_cloud_cover. The tool description adds context about the tile selection ('least-cloudy') and cache usage, but does not add new parameter-level semantics, so the baseline of 3 applies.

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 clearly states the action ('Fetch'), the specific resource ('least-cloudy Sentinel-2 L2A tile covering a given H3 cell'), and the source ('Microsoft Planetary Computer'). It also distinguishes itself by enumerating the returned bands and noting the cache behavior for subsequent perception_classify or perception_embed calls.

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 implies when to use this tool by noting the tile is cached for subsequent perception_classify or perception_embed calls, which gives contextual placement among siblings. It does not explicitly state when not to use it or name an alternative, but the guidance is sufficient for typical usage.

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