list_delivery_failures

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

No annotations are provided, so the description must convey behavior. It clearly indicates a read-only operation (list) and specifies the criteria (recent, outgoing, failed/pending/recovered). It doesn't mention side effects, but as a listing operation, it's reasonably transparent. It could be clearer about whether it modifies anything, but it's unlikely given 'List'.

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 (two sentences) and directly states the purpose and use case. No unnecessary words or redundancy.

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 description provides sufficient context for the tool's behavior and purpose. Since there is no output schema, the description does not explain the return format, but it's implied that it returns a list of delivery failures. The absence of explicit output details is a minor omission but not critical for this simple tool.

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?

Each parameter (limit, hours_ago, include_pending) has a descriptive explanation in the schema, covering 100% of parameters. The descriptions are clear enough for a user to understand their purpose, though 'include_pending' could be more precise about the condition 'error is 0'.

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 the tool's function: listing recent outgoing messages that failed, are pending, or potentially recovered via SMS/RCS fallback, with a concrete use case (finding red 'Not Delivered' bubbles). This distinguishes it from sibling tools like read_recent_messages or search_messages.

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 provides a specific use case ('Use this to find red Not Delivered bubbles'), which implies when to use it. However, it does not explicitly mention when not to use it or compare with alternatives, but the purpose is narrow enough that this is not a major gap.

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