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

Annotations already declare the important traits: a non-read-only mutation that is idempotent, non-destructive, and closed-world. The description adds only the authorization scope ('the caller's'), and says nothing about behavior for an already-read notification, an unknown id, or what the call returns. Annotations carry most of the weight here.

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?

One short sentence with no filler and the scope ('caller's', 'one of') front-loaded. It is efficient but borders on under-specified rather than maximally informative.

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 one-parameter, no-output-schema notification mutation with full annotation coverage, the description covers what is needed to invoke correctly. Only edge-case outcomes and the id's provenance are missing, which are minor for this complexity level.

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?

There is a single parameter with 100% schema coverage ('Notification id'), so the schema already fully documents it. The description adds no format, source, or sourcing hint (e.g., that ids come from list_my_notifications), so baseline 3 applies.

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 plus resource ('Mark ... as read') scoped to 'one of the caller's notifications', which implicitly separates it from the bulk sibling. It never names mark_all_notifications_read outright, so differentiation is inferential rather than explicit.

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 phrase 'one of the caller's notifications' implies this is the single-item counterpart to mark_all_notifications_read, but no when-to-use rule or alternative is stated. An agent must infer the split from the tool name alone.

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