Get a library statistic

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

With no annotations provided, the description carries full behavioral burden. The verb 'Get' and the term 'pre-aggregated' clearly indicate a read-only operation that returns a chart, and it clarifies the scope (library-wide, not user-specific). It stops short of mentioning side effects or auth, but for a read operation this is acceptable.

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 front-loaded with a clear purpose, then uses structured lists to present the many 'kind' options efficiently. The prose is concise and each sentence adds information. The long list is necessary given the schema enum, so this is appropriately sized.

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's moderate complexity, no output schema, and 4 parameters, the description provides a complete picture: full kind enumeration, optional libraryIds restriction, and parameter scoping. The absence of return format details is a minor gap but does not hinder selection or invocation.

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 baseline is 3. The description adds value beyond the schema by grouping the 'kind' options into meaningful categories (Distributions, Top-N, Timelines, Relationships, Metadata health) and explicitly states that 'granularity' and 'range' apply only to books-added-over-time, which is not apparent from the schema alone.

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 uses a specific verb ('Get') and resource ('pre-aggregated, library-wide statistics chart'), and explicitly contrasts with sibling tools ('not the user's personal reading — use get_reading_statistic for that; for headline totals use get_library_stats'). This makes the tool's purpose unambiguous and distinguishes it from alternatives.

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?

Provides explicit when-not guidance by naming alternative tools for personal reading and headline totals. It also clarifies that 'granularity' and 'range' apply only to books-added-over-time, giving concrete direction on when to use these parameters.

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