chat_activity

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, so 'Read-only with no side effects' restates structured data rather than adding to it. The ranking/derived-metric behavior is useful context, but no new behavioral traits (ordering guarantees, staleness, empty-result behavior) are disclosed beyond what annotations provide.

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 blocks, front-loaded with the purpose and followed by routing guidance; nothing is bloated. The only minor waste is the read-only sentence, which duplicates the annotations and could be dropped without losing information.

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 re-explained, and the description covers purpose, ranking semantics, usage intent, and the sibling alternative. For a single-optional-parameter read tool, nothing an agent needs to invoke it correctly 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?

Schema description coverage is 100% and the single limit parameter is fully documented with range and default in the schema. The description contributes no additional meaning about pagination, defaulting, or how limit interacts with ranking, so the baseline 3 applies.

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 gives a specific verb (List), resource (Signal chats), and scope (ranked by recent activity), plus the exact fields surfaced: last message date, last reply date, and count of unanswered inbound messages. It also explicitly distinguishes itself from list_chats, which allows an agent to route correctly without inspecting either 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?

It states the intended task ('Use this to identify chats that need a response') and names the alternative plus the condition that selects it ('Use list_chats instead for a general chat directory with message previews'). Both the when-to-use and the when-to-use-something-else paths are explicit.

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