Mark message read

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

Annotations already declare idempotentHint=true and destructiveHint=false, but the description adds substance beyond them: the message stays in the vault and in full history, so the state change is scoped to inbox visibility only. It also discloses the return contract ({ success: true, id }) and the exact error case ('Message not found' for an unknown id or non-message note).

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?

Four short sentences, front-loaded with the effect and followed by the trigger, idempotency guarantee, and return contract. No sentence is filler; each adds a distinct fact an agent needs.

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 mutation tool with annotations and no output schema, the description covers trigger, durability of the change, repeat-safety, return shape, and failure mode. Nothing required 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?

Schema coverage is 100% and the schema already specifies that the id comes from brain_messages_get with an example format, so the description adds no new parameter detail. Baseline 3 applies when the schema carries the parameter semantics.

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 and resource ('Mark one message as read') plus the observable effect: it disappears from the default unread inbox returned by brain_messages_get. That explicit link to the sibling tool lets an agent distinguish it from brain_messages_get or brain_messages_send without opening a 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?

'Call it after you have handled a message' gives a clear trigger condition, which implicitly excludes marking messages as read before processing them. It stops short of naming alternatives or an explicit when-not, but for a single-purpose one-parameter tool the guidance is actionable.

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