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

With no annotations at all, the description carries the full burden and does real work: it discloses the returned fields, notes readings are 'current', and explains the failure mode for sources under non-commercial, restricted, or unreviewed licences (an error naming the licence). It still omits auth requirements, rate limits, and pagination behavior for the limit parameter.

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 sentences, zero filler, and the payoff (what you get back) is front-loaded ahead of the edge case (licence refusals). The provenance parenthetical is information-dense rather than redundant.

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 17-parameter tool with no annotations and no output schema, the description compensates well by describing the return shape in lieu of an output schema and flagging the licence-error path. Remaining gaps are the absence of auth/rate-limit guidance and any note on how narrow the parameter set is per source.

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%, and every parameter (including source-specific ones like usgs, bbox, coops, elevated, window) is documented inline with source applicability and examples. The description adds only the vague hint that one source is selected, so the 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 ('Fetch current readings') plus scope ('from one source'), and enumerates what each reading contains (value, unit, summary, place, provenance). That scope word cleanly separates it from the list_*/search_* siblings and from get_source/get_layer, which imply metadata or layered data rather than point readings.

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 never says when to reach for this tool versus get_source, get_dataset_part, or get_layer, nor does it state prerequisites such as needing a fetchable source id first. The only conditional text is about licence-error responses, which is error behavior, not usage routing.

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