NASA Trek map tile (Mars, Moon, Vesta)

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

Annotations already carry readOnly/idempotent/destructive/openWorld hints, and the description adds real context beyond them: it reads the layer's WMTS capabilities to validate the tile and pick the format, and it notes no API key is needed. These are concrete behavioral facts not present in the structured fields.

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?

Front-loads the return value, then qualification and sourcing in tight sentences with no filler. Slightly dense but every clause is informative; nothing wasteful.

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?

Covers layer sourcing, both addressing schemes, format validation and auth, which is enough for a tile-fetch tool. No output schema is needed since the return is an image, and annotations cover the safety profile; only the explicit prerequisite ordering with nasa_trek_layers 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 schema documents all 8 parameters (including the equirectangular-only lat/long note). The description restates the addressing dichotomy (zoom/row/col vs lat/long) but adds no syntax or format detail beyond it, so baseline 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?

States a specific verb and resource ('One WMTS map tile image from NASA Mars Trek, Moon Trek or Vesta Trek'), and names the source of valid layer IDs (nasa_trek_layers), cleanly separating it from that sibling. An agent can tell what it returns without opening the schema.

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?

Mentions that the layer comes 'from nasa_trek_layers' and gives the two addressing modes, which implies the workflow, but never states explicitly to call nasa_trek_layers first or when-not to use this tool. Usage is implied rather than instructed.

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