List chats

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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds behavioral details beyond that: 'most recent first, with unread state' and the distinction between two kinds of chats. It does not mention pagination or result limits, but for a simple list tool with open-world semantics, this is adequate and adds real context.

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 sentences with no filler. The first sentence defines the scope and ordering, the second gives actionable routing instructions. Every word earns its place; it is front-loaded with the core purpose.

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?

Given there is no output schema, the description carries the burden of explaining what the tool returns. It covers the two chat types, ordering, unread state, and how to consume the returned id. It doesn't mention pagination or field details, but for a list tool this is sufficient for an agent to call and use it correctly.

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?

The tool has zero parameters, so the schema covers everything trivial. The description doesn't need to explain parameters and adds no parameter-specific meaning. Baseline for 0 params is 4; the description correctly focuses on output and usage rather than params.

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: 'The user's Substack chat inbox: publication chats they belong to and direct messages' – it clearly defines what the tool lists. It also distinguishes itself from siblings like get_chat_threads and read_dm by describing the overall inbox vs. per-thread operations.

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?

Explicitly names alternatives and the condition for using them: 'Use the returned id with get_chat_threads (publication_chat) or read_dm (direct_message).' This tells the agent exactly how to route based on the item type, leaving no ambiguity about when to use this tool versus its siblings.

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