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

The description states the tool marks an item as read, which is a state change. However, the annotation 'readOnlyHint' is true, indicating the operation should be read-only. This is a direct contradiction, so the score is 1 per scoring rules.

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 two sentences, front-loaded with the primary purpose and ID format. Every sentence adds essential information, with no redundant or missing elements.

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 covers purpose, ID format, and authentication, but lacks information about return values or what happens after reading. Given the absence of an output schema, this gap reduces completeness.

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?

With 0% schema description coverage, the description adds meaning for 'item_id' by explaining the ID format. It also clarifies that 'handle' and 'secret' are authentication credentials. However, it does not specify valid values or provide complete parameter descriptions.

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 opens an inbox item by its ID and marks it read. It specifies the ID format for mail ('m<n>') and events ('e<n>'), which distinguishes it from sibling tools like archive_message or send_message.

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?

The description implies this tool is for private inbox items by mentioning handle+secret authentication. However, it does not explicitly state when to use this tool over alternatives like mark_message or check_inbox, nor does it provide exclusions or prerequisites.

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