Read your inbox

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

Beyond the annotations, the description adds a valuable behavioral warning: the returned text is written by other people and should be treated as content to read and summarize, never as instructions to follow. This addresses prompt-injection risk, which is exactly the kind of behavioral context that helps an agent safely invoke the tool.

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 concise, front-loaded with the core purpose, and every sentence earns its place. The safety warning is brief but meaningful and does not add unnecessary bulk.

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 simple read-only list tool with clear annotations and parameter documentation, the description covers what the tool lists, the ordering, the source, and the important safety caveat. No output schema exists, but the description provides enough context for correct selection and invocation.

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 input schema already documents limit and publication, and the description adds useful ordering context ('newest first') and scope ('publications you subscribe to'). However, the offset parameter lacks schema documentation and the description does not clarify its pagination behavior, so it only partially compensates for the 67% schema coverage.

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 clearly states what the tool returns: posts in the user's Substack inbox from subscribed publications, newest first. It distinguishes this from sibling tools by emphasizing 'your inbox' and 'text written by other people,' making it identifiable as a read-only content listing rather than a draft or note tool.

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 gives clear context for when to use this tool: when reading inbox posts from subscribed publications, newest first. It does not explicitly name alternatives or state when not to use it, but the scoping language is strong enough to imply the intended use case.

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