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

Annotations already declare destructive=true and idempotent=true. The description adds meaningful context beyond that: deletion affects both parties, is immediate and permanent, and has a specific exception for pending owner decisions. It does not cover every operational detail, but it substantially improves behavioral understanding.

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 short, front-loaded with the core action, and each sentence adds useful scope or exception detail. There is no redundant or filler language.

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 destructive message-deletion tool with full schema descriptions and rich annotations, the description provides enough context to call it correctly. It explains the bilateral permanent effect and the pending-decision exception, so no critical behavioral information 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%, so parameter meaning is already fully documented in the input schema. The description does not add parameter-specific semantics beyond what the schema provides, which is acceptable at baseline 3.

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: delete a private message. It also clarifies scope and eligibility ('sent or were sent', 'for both of you', 'For members'), making it distinguishable from sibling messaging tools.

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 clearly establishes when this tool applies: deleting a private message the caller sent or received. It also names a specific exception for messages pending owner decision. It does not explicitly compare against alternative tools, but the context is clear.

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