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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real behavioral context: it serves only STORED results and never recomputes or triggers AI work, it describes the ambiguous-lookup fallback, and it warns that digest content is untrusted customer-derived data rather than instructions. Those are traits no annotation conveys.

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 the core action and payload, then addressing rules, then the untrusted-data caveat. Three dense sentences with little waste, though the middle addressing sentence packs several conditions into a long clause.

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?

For a zero-required-parameter read tool with an output schema, the description covers purpose, addressing semantics, non-recomputation behavior, disambiguation fallback, and a safety note on untrusted content. The output schema handles return-value detail, so nothing essential is missing.

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?

With 0% schema description coverage, the description carries the parameter burden and does so well, explaining the distinct roles of definition_id, name, and chat_id and the conditional behavior when only chat_id is supplied. It does not address what happens if both definition_id and name are given, nor chat_id format expectations.

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 ('Read a chat digest's prepared answer') and enumerates exactly what the payload contains (answer, key points, evidence with message ids, entities, freshness, coverage counts). This clearly separates it from sibling list_chat_summaries, which enumerates rather than returns a prepared digest.

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 concrete addressing rules: use definition_id or name to target a definition, and chat_id alone works only when the chat has exactly one definition, otherwise matches are returned for disambiguation. It also points to list_messages for evidence sources. It does not explicitly say when to prefer this over list_chat_summaries, which keeps it short of a 5.

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