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

Annotations already declare readOnlyHint and idempotentHint, so the description isn't needed for safety signaling. The description adds valuable context beyond annotations: the data-sampling caveat ('Observed readers are sampled graph observations and are not total readership') and access-tier limits with a link. These are genuinely useful behavioral disclosures for an agent relying on the data.

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 short sentences with no filler. The purpose is front-loaded, followed by the data caveat and access information. Each sentence earns its place, and the structure is easy to scan.

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?

For a single-parameter read tool with an output schema and readOnly/idempotent annotations, the description covers the essential bases: purpose, data-fidelity caveat, and access constraints. The only notable omission is guidance on how to discover or validate a fiction ID, which is minor given the tool's simplicity and the presence of 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 0% for rr_fiction_id, so the description carries the burden of explaining the parameter. The description clarifies that rr_fiction_id is a 'Royal Road fiction ID' and implies single-ID lookup, which adds meaning over the bare integer schema. However, it doesn't explain the ID's format, range, or how to obtain one, leaving a partial gap.

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: 'Get Scrykeeper intelligence for one Royal Road fiction ID.' The phrase 'one ... fiction ID' clarifies the tool's scope as single-story lookups, which helps distinguish it from search_market and get_author, though it doesn't name sibling tools explicitly.

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?

No guidance is provided about when to use this tool versus alternatives like get_author or search_market. The description offers access-tier information but doesn't state conditions like 'use when you have a specific fiction ID' or 'use search_market to discover IDs.' The agent must infer usage from the purpose alone.

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