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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds context that the tool explains scope and supported decision states, which is useful but does not go beyond what annotations already provide. No contradiction with annotations.

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 description is a single, clear sentence that front-loads the tool's purpose. It is appropriately sized for a zero-parameter informational tool, though it could be slightly more specific about the decision states it covers.

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?

Given the tool has no parameters, an output schema exists, and annotations cover safety, the description is largely complete. It explains the tool's scope and purpose, which is sufficient for an agent to decide whether to call it. A minor gap is that it doesn't enumerate the supported decision states, but the output schema likely covers that.

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 has zero parameters, so the schema is trivially complete. The description correctly focuses on the tool's informational purpose rather than parameter details. Baseline 4 is appropriate for a zero-parameter tool.

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?

The description states a specific verb ('Explain') and a clear resource ('UK Skilled Worker sponsor-change checker scope and supported decision states'). It distinguishes itself from sibling tools like assess_change_impact and list_supported_change_events by focusing on explaining the checker's scope and decision states rather than performing an assessment or listing events. However, it could be slightly more explicit about what the tool does not do.

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 implies the tool is for understanding the checker's scope and decision states, which suggests it should be used when an agent needs background information before using assess_change_impact or list_supported_change_events. However, it does not explicitly state when to use this tool versus its siblings, nor does it provide exclusions or alternative routing.

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