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

Annotations already declare readOnlyHint/idempotentHint true and destructiveHint false, so safety is covered. The description adds material behavior the annotations do not: the response format (JSON-stat2 with labeled dimensions and numeric values), the backing host (px.hagstofa.is), no-auth requirement, and CC BY 4.0 licensing. It stops short of noting response-size or pagination behavior for large 'all' selections.

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 what the tool does, then the prerequisite, then the response format, then the example and provenance details. Every sentence carries actionable information — no filler, no restatement of the title.

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?

An output schema exists, so return values need not be spelled out, yet the description still names JSON-stat2. Prerequisite discovery tool, parameter semantics, example call, data source, auth, and license are all present. Nothing an agent needs to invoke this correctly 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 baseline is 3; the description earns a modest bump by illustrating how the nested filter/values semantics combine in a real query ('Ár filter=top values=[3]' for the 3 most recent years) and by warning that dimension codes are Icelandic words with non-ASCII characters. Much of this duplicates schema text, so it does not rise above 4.

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 ('run a statistical query against an Iceland statistics table') and scopes it precisely to dimension-filtered slicing. Clearly distinguished from its sibling table_metadata, which the description positions as the discovery step. An agent can identify this tool's role 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?

Explicitly instructs 'Call iceland-statistics.table_metadata first to discover valid dimension codes and value codes', naming the prerequisite and the reason. It also supplies a worked example (Eining='0', Ár filter='top' values=['3']) that shows exactly how the described usage translates into a call.

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