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

Annotations already declare destructiveHint=false and idempotentHint=false; the description usefully reinforces additive semantics ('nothing is replaced or removed') and implies a hard prerequisite on an existing word. It does not say what happens on a duplicate meaning, whether the word_id must belong to the caller, or what an invalid word_id yields.

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?

Two short sentences, zero filler, with the core action and the additive constraint front-loaded.

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?

An output schema exists, so return values need not be explained, and the annotations cover the safety profile. What remains missing for a nested-object mutation tool is duplicate/error behavior and whether appended meanings affect ordering, which matters given the reorder_meanings and remove_meaning siblings.

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 only 50%, but the nested object's fields (meaning, gloss, examples) are well described in the schema itself. The description contributes real meaning by stating the meaning must be in the notebook's meaning language and that examples ride along with it, though it says nothing about word_id sourcing beyond the schema's own note.

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?

Specific verb (adds) plus resource (one meaning) plus scope (a word already in the notebook), with the 'only adds, nothing replaced or removed' clause implicitly separating it from update_meaning and remove_meaning. It never names those siblings outright, so the differentiation is inferred rather than stated.

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?

'To a word already in the notebook' implies the prerequisite that the word must exist (create it with add_word first) and hints at when to use this over update_meaning. There is no explicit when-to-use/when-not statement or named alternative, so the agent must infer.

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