Extract recent messages from a chat

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the description does not need to restate them. It adds substantial behavioral detail: the coverage object with 'asked Xh, have Yh', truncation that drops older messages when the budget is exceeded, the sync-cache limitation, and the note that message bodies are user-authored content. This goes well beyond the annotations.

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?

The description is about five sentences but each adds value: main purpose first, then coverage summary, truncation policy, cache caveat, and a safety note. It is front-loaded with the core action and avoids redundancy. The length is justified by the behavioral complexity.

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?

The tool has moderate complexity (3 params, truncation, cache behavior) and an output schema, so the return format is defined. The description covers the main behaviors—time window, coverage, truncation, cache—well. The only missing piece is the meaning of `include_deleted`, which is not clarified in either the schema or description, leaving an agent to guess its effect.

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 0%, so the description must compensate. It explains the `hours` parameter (range 1-168, default 24) but does not clarify `include_deleted` or give additional semantics for `chat_id` beyond its obvious meaning. Two of three parameters remain effectively undocumented beyond the schema, which is a significant gap given zero schema descriptions.

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?

The description states a specific verb and resource: 'Returns every message from one chat (by chat_id) within the last N hours'. It clearly distinguishes itself from siblings like read_chat (which likely returns all messages) and search_messages (which filters by terms). The time-window scope is explicit, making it unambiguous what this tool does.

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 description conveys when to use the tool (for time-bounded extraction from a single chat) and provides relevant context (the sync cache means older messages may be absent). However, it does not explicitly name alternatives or state when not to use this tool versus siblings, leaving some choice to inference.

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