message_list

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

Annotations already mark this as read-only and non-destructive. The description adds meaningful context beyond those annotations: the tool is deprecated, still functional, and not intended for new work. It also clarifies that it returns full history rather than only unread messages. This exceeds the minimum expected from a read-only 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 front-loaded with the critical deprecation warning, then states purpose, usage, alternative, and parameter details in a compact, scannable structure. Every sentence contributes useful information without 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?

For a low-complexity tool with two optional parameters, full schema coverage, an output schema, and safety annotations, the description covers deprecation status, scope, appropriate use, and the sibling alternative. Nothing needed for correct selection or invocation 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 the input schema already fully documents both parameters. The description repeats the same semantics for read and limit without adding syntax details, defaults, or constraints beyond what the schema already provides. Baseline 3 is appropriate.

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 'List all messages sent to or from you (full history, not just unread)', which names a specific verb, resource, and scope. It also distinguishes itself from message_inbox by contrasting full history versus unread-only.

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?

Provides explicit when-to-use guidance: review past conversations, check for missed messages, or audit communication. It also names the alternative condition directly: 'For unread-only, use message_inbox() instead.' No inference is required.

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