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

Goes well beyond the annotations by disclosing that existing explanations are overwritten ('replaced' when one already existed), that everything else is preserved, the 40-item batch cap, and partial-failure semantics via 'skipped' with reasons. It stops short of saying whether an overwritten explanation is recoverable or what permission/state (e.g. published vs draft) the write requires.

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 purpose, then usage exclusions, then limits, then return shape — every clause carries real routing information. It loses a point for dense nested negatives ('Asking when explanations are shown...is not asking to write them') that take effort to parse.

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?

No output schema exists, and the description compensates by explaining the result contract: 'written' for items that got an explanation, 'replaced' for ones that already had one, and 'skipped' with reasons. Combined with the batch limit and the do-not-fill policy, an agent has everything needed to call this correctly and interpret the response.

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 description coverage is 100%, so 'item' (verbatim text identifying the item in get_activity_content) and 'explanation' (one or two informative sentences, never just "Correct!") are already documented. The description only restates the 40-item cap that maxItems already encodes, adding no new meaning beyond the schema. Baseline 3 is correct here.

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 object ('Write or rewrite the explanation of items that already exist') and immediately bounds the scope by naming what is left untouched (texts, images, audio, explanation media). An agent can distinguish it from set_activity_content and change_item_explanations without opening any schema.

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?

Gives an explicit trigger ('ONLY when the user asked to add, write or change explanations...they name, or of all of them'), explicit negatives ('never set_activity_content "replace" for that', 'never rewrite an existing explanation' when only display timing is asked, 'never fill the items that have none, offer it instead'), and names the correct alternative (change_item_explanations). This is about as complete as when-to-use guidance gets.

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