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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered; the description adds real behavior beyond that: what happens when no goal exists (it says so and proposes one from past reading) and that the tool is non-mutating. It does not mention auth or rate limits, but for a local read-only tool those are minor.

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?

Front-loaded with what the tool returns, then the no-goal fallback, then the usage trigger — a sensible ordering with no filler. The enumerated return fields partially duplicate the output schema, which is the only wasted space.

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 an output schema present, the description needn't explain return values, and annotations cover the safety profile; the single optional param is fully documented in schema. What remains is that year-scoping behavior (e.g., querying a past year's goal) is never addressed in prose.

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?

Only one parameter and schema coverage is 100%, with the default (current year) documented in the schema itself. The description never mentions the year parameter, so it adds no semantics beyond the schema — baseline 3 applies.

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?

States a specific verb and resource (yearly book goal + progress) and enumerates exactly what is reported: books finished, books left, on-track status, required pace, books per month. It also draws a hard boundary — 'It does not set a goal' — which separates it from any goal-mutation tool, and the yearly-goal framing distinguishes it from get_reading_stats and get_reading_trajectory.

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 'Use when...' sentence gives three concrete user phrasings (how am I doing on my goal, am I on track, how many books this year) that map cleanly to invocation. The exclusion 'It does not set a goal' is stated, but no sibling is named as the alternative for adjacent questions like general reading stats or monthly summaries.

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