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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds value by disclosing the shape of the return payload (date ranges, tile grid, legend URLs, raw WMTS template), which matters because there is no output schema, but it says nothing about auth requirements, rate limits, or failure modes for unknown layer IDs.

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 purpose is front-loaded in the first clause and the routing instruction is a compact final sentence. The middle enumeration of return fields is long but each item is load-bearing since no output schema exists to carry that information.

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?

With no output schema, the description correctly compensates by enumerating the returned fields, and the projection parameter's effect is documented in the schema. It is nearly complete for a read-only lookup, though it omits what happens when a layer identifier is invalid or the projection is unsupported.

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%: the layer example and the projection enum values (epsg4326/3857/3413/3031) are already documented in the schema. The description adds no syntax, format, or defaulting information beyond what the schema provides, 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?

States a specific verb and resource ('Everything NASA GIBS publishes about one imagery layer') and enumerates exactly what is returned: title, date coverage as ISO 8601 ranges, latest date, tile grid/zoom, format, extent, colour map/legend URLs, WMTS template. This is clearly distinguishable from gibs_list_layers (enumerate layers) and gibs_tile_url (build a tile URL).

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?

Explicitly states 'Call this before gibs_tile_url when you need to know which dates exist for a layer', giving both an ordering constraint and the condition that selects it. The layer parameter description also routes the agent to gibs_list_layers for obtaining an identifier, so both sibling relationships are covered.

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