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

Adds context beyond annotations: explains that nothing is written to the thread, no one is notified, and it does not spend the daily allowance. Also explains the remove parameter behavior. This goes beyond the idempotent/read-only hints.

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, front-loaded with purpose and parameter behavior, then behavioral notes and alternative. No wasted words.

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?

Complete for a simple bookkeeping tool: covers purpose, parameter behavior, resource impact, and alternative. Output schema exists, so return values need not be described.

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 has no descriptions (0% coverage), so the description compensates by explaining the remove parameter ('remove=true clears it') and implying message_id through 'mark that you read a message'. Adds meaning beyond the schema.

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?

States a specific verb ('Mark') and resource ('that you read a message'), and distinguishes from board_answer by saying 'Use board_answer to mark an actual answer.' Clear and specific.

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 the alternative tool (board_answer) and the condition that selects it (actual answer). Also gives context that it's personal bookkeeping with no thread writes or notifications, making the usage clear.

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