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

Annotations already declare the safety profile (destructiveHint=true, idempotentHint=true, readOnlyHint=false), so the agent knows this is a repeatable state mutation. The description adds useful scope qualifiers ('every unread', 'signed-in account', 'in-app'), but does not explain that the change is irreversible or that no undo exists, which is exactly what the destructiveHint is flagging.

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, zero filler, scope stated first and the disambiguation last. Every clause 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?

Output schema exists, so return values need not be described, and annotations cover the mutation/idempotency profile. For a zero-parameter bulk action, nothing an agent needs to call it correctly is missing.

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?

The tool takes zero parameters, so the baseline is 4; there is no parameter syntax the description could or should explain. The description correctly avoids inventing filters and reiterates the account-level scope instead.

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 ... as read') and resource ('every unread in-app notification in the signed-in account'), and explicitly names the sibling it differs from (mark_notification_read). An agent can distinguish bulk vs. single-target behavior without opening either schema.

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 routing: this tool for all notifications, with the alternative (mark_notification_read) named and the condition that selects it ('for one notification'). No inference required.

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