mark-as-unread

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

No annotations are provided, so the description carries the burden. It discloses the return value (a confirmation) and implies the mutation by stating the tool marks a message unread. However, it does not explicitly state permission requirements or reversibility, though these are less critical for this action.

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 and well-organized: starts with use case, then returns, then exclusions and prerequisites. Every sentence adds value, and it front-loads the most critical information.

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 single-parameter tool with an output schema, the description covers the core action, exclusions, return value, and id source. It is complete for the tool's complexity and leaves no significant gaps.

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 0%, so the description must compensate. It explains the id parameter's role ('by id') and tells the user where to obtain it, adding context beyond the bare schema pattern.

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 uses specific verb+resource: 'marking a single message (by id) as unread'. It clearly distinguishes from sibling tools like mark-as-read and batch-mark-as-unread by explicitly naming them in the 'Do not use when' clause.

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, do-not-use scenarios with named alternative tools (batch-mark-as-unread, mark-as-read), and even notes the prerequisite to get the id from search-messages or list-messages first.

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