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

Annotations already establish readOnly/idempotent/non-destructive/openWorld, but the description adds real value beyond them: it discloses that no API key is required and describes what each mode returns (one-line list plus start page and key instructions; full guide with inputs, execution, outputs and cost). It stops short of noting any limits, but with annotations covering the safety profile this is solid.

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?

Three parallel sentences, each mapping to one parameter state, with the most important fact ('No key needed') front-loaded. No filler; every clause carries behavioral or routing information.

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?

Zero required parameters, no output schema, read-only. The description compensates by describing the return payload for each of the three modes, so an agent knows what to expect from every invocation shape without needing an output schema.

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 coverage is 100% so the baseline would be 3, but the description goes further by explaining the conditional interaction between the two parameters (what happens with neither, one, or the other) and by enumerating the disappearance of customer_type to trigger list mode. That is meaningfully more than the schema's terse per-parameter notes.

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 names the resource (guides) and spells out three distinct behaviors selected by parameters: list mode, full-guide mode, and template mode. This is specific enough that an agent can distinguish it from siblings like 'capabilities' or 'account' 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?

It gives clear conditional usage: omit customer_type for the list, supply it for the full guide, use template for script text, and notes no key is needed. It does not compare against sibling tools that might also serve as entry points (e.g. 'capabilities'), so the routing guidance is good but not exhaustive.

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