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

Annotations only declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description goes beyond this by disclosing that the tool requires a sign-in the connection lacks, so it will not return actual data but rather an error with resolution guidance. This is essential behavioral context not present in 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?

Two sentences, front-loaded with the key constraint (sign-in issue) and the return behavior. The second sentence tells the agent exactly when to invoke and what to expect. No filler words.

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 zero parameters and no output schema, the description covers everything needed: it explains the tool's intended function, its limitation, and the appropriate action. An agent can confidently call it based on this text alone, even among many siblings.

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?

There are zero parameters, so schema coverage is 100% trivially. The description doesn't need to explain parameters. Per calibration, 0 params gives a baseline of 4. The description adds no parameter info because none exists, so a 4 is appropriate.

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 and resource: 'returns the reservations arriving on a day,' and immediately clarifies the caveat about sign-in. This distinguishes it from siblings like departures and day_summary by focusing on arrivals. It also explains the actual behavior in this connection (returning an error and fix guidance), which is a clear purpose.

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 gives explicit when-to-use instruction: 'Call it anyway when the user asks for this.' It also explains why it should still be called—because it provides helpful error and fix information. It doesn't mention alternatives, but the instruction is unambiguous and covers the expected scenario.

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