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

Annotations already indicate not readOnly, not idempotent, not destructive, which is somewhat contradictory (marking read is idempotent, but annotation says false). The description adds the behavioral nuance of timing (after action, not first sight), which is valuable. However, it doesn't mention that marking read is irreversible per se or what happens if called again. There is a minor inconsistency: readOnlyHint false implies mutation, but no details on side effects beyond the unread queue.

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, tightly packed with the essential usage rule. It front-loads the purpose and then gives the critical timing guideline. No filler words; every sentence earns its place.

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?

Given the tool has one parameter, full schema coverage, and no output schema, the description covers the key usage context (when to mark read, what it affects). It doesn't mention the effect of idempotency (repeated calls) or whether it returns anything, but for such a simple tool, the description is nearly sufficient. The only minor gap is that it doesn't explicitly state the input source (list_notifications ids), but the schema already does that.

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 coverage is 100% and the 'ids' parameter is well-described in the schema (from list_notifications). The description doesn't add any extra meaning, but since the schema is complete, baseline 3 is appropriate. No additional semantic insight is provided beyond what the schema already gives.

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 verb ('mark') and resource ('your own notifications') and the effect (leaving the unread queue). It distinguishes from siblings like list_notifications and mark_inbox_conversations_read by focusing on the user's own notifications. Slight deduction because it doesn't explicitly mention output or return value, but purpose is clear.

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 gives explicit guidance: mark read only after action is taken, never on first sight. This is a clear behavioral rule that helps an agent decide when to use it, and by implication when not to (e.g., before acting). This goes beyond vague context and provides a direct conditional.

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