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

Annotations already declare a safe idempotent read, so the bar is lower; the description nonetheless adds real behavioral context: the check runs daily, it reflects live HTTP status and record counts, and pre-deadline all registers report 'expected'. That pre-deadline caveat is exactly the kind of non-obvious state an agent needs to interpret results.

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-loaded with the purpose, then the legal citation, then the pre-deadline caveat. Every sentence earns its place except the parenthetical regulation citation, which is heavy detail for an agent deciding how to call the tool but is at least contextually relevant.

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-field explanation is unnecessary; the description still names the returned fields, and adds cadence, legal basis, and the pre-deadline 'expected' state. Nothing an agent needs to invoke or interpret this zero-argument tool 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?

The tool takes zero parameters, so there is no parameter semantics to explain; baseline for a no-param tool is 4. Nothing in the description conflicts with the empty schema.

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 (daily availability check) and a precise resource (national registers of relying parties), and enumerates the returned dimensions: status per country, last check, HTTP status, record count, 7-day uptime. This is clearly distinguishable from siblings like get_country or get_deadlines, which cover different resources.

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 establishes context (a daily availability check of register endpoints) but never states when to call this versus get_country or get_deadlines, nor any exclusions or prerequisites. Usage is implied by the subject matter rather than explicitly guided.

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