Summarise group activity

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a genuinely useful behavioral note ('Deterministic stats; the assistant can write prose on top'), clarifying that output is reproducible and that prose generation is the caller's job. However, it never defines the window that 'recent messages' covers, which materially affects 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?

Two dense sentences, front-loaded with the core purpose, then the output inventory, then the determinism/prose caveat. No filler and nothing repeated from the schema or annotations.

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?

With no output schema, the description usefully substitutes by listing the digest's contents, and the annotations cover safety. The remaining gaps are the undefined 'recent' time window and the unspecified default/interpretation of 'count', which an agent would need to resolve before calling.

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% and the description mentions none of the three parameters. 'count' (bounded 10-500) has an unspecified default and an ambiguous meaning (message count vs. digest length), and 'timezone' is never explained relative to 'busiest hours' — a real semantic gap for a tool whose headline output is a time-of-day distribution.

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 ('Activity digest for a group from its recent messages') and immediately enumerates the dimensions of the digest: volume, active members, busiest hours, keywords, unanswered questions, shared links. This is clearly distinguishable from the raw sibling read_group_messages, since it is an aggregate rather than a message fetch.

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?

No explicit when-to-use or when-not guidance and no sibling is named. The phrase 'from its recent messages' implies it is a downstream/analysis tool rather than a raw read, but the agent must infer that read_group_messages is the alternative when raw messages are wanted.

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