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

Goes beyond the annotations by disclosing upsert semantics (existing word moves to top, only new meanings are added), the fact that everything except the headword is optional, and the language-pairing constraint between meanings and examples. This genuinely tells the agent what happens to existing data, which annotations alone (destructiveHint=false, idempotentHint=false) do not convey. It does not cover error/permission behavior.

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?

Purpose and the card inventory are front-loaded in the first sentence, with the upsert rule last. The long clause listing card fields is dense but earns its place as a completeness cue; minor redundancy with the schema's own field list keeps it from a 5.

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?

A 16-parameter mutation tool with an output schema and annotations that already declare the safety profile; the description supplies the missing behavioral layer (defaults, upsert, language constraints). Nothing essential for correct invocation is absent, though guidance on choosing this over add_meaning/update_word would close the remaining gap.

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 88%, so the schema already documents nearly every field including the language codes and the notebook_id default. The description adds only the optionality statement ('everything but the headword is optional') and the meaning/target language split, which the schema largely repeats. Baseline 3 fits.

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?

Names a specific verb+resource ('Saves one word or phrase ... to their notebook') and enumerates the card contents, so the agent knows exactly what gets created. It also discloses the upsert behavior ('If the notebook already has the word, it moves to the top'), which implicitly separates it from add_meaning and update_word, though those siblings are never named.

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?

Usage is implied by 'the user asked to save', and the upsert sentence tells the agent it is safe to call for an existing headword. However, there is no explicit routing guidance such as 'to add a meaning to an existing word, use add_meaning' or 'to change an existing card, use update_word', which matters with 17 sibling tools.

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