mark_message_read

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

Discloses behavior annotations do not cover: the returned fields, the repeat-call semantics (first read time retained, activity time refreshed), and the NOT_FOUND error condition. With readOnlyHint=false the mutation nature is already flagged, and the description enriches it rather than contradicting it.

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?

Five compact sentences, front-loaded with the core action and return value, followed by edge cases and the alternative tool. No filler and every sentence carries distinct information.

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?

With no output schema, the description compensates by naming the return fields (message_id, read, read_at), and it covers the error path and the sibling-tool boundary. An agent has everything needed to call it correctly.

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 description coverage is 100%, so all three parameters are documented in the schema. The description adds only implicit scope ('received message' implies you must be a recipient) and no format or syntax detail beyond that, so the 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 (mark read) and resource (one received message), plus the key differentiator that it does not acknowledge it. The agent can distinguish this from acknowledge_message and fetch_inbox without opening any 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?

Explicitly routes: use acknowledge_message when ack_required is set, and notes fetch_inbox already marks messages unless mark_read:false. It also states the failure precondition (NOT_FOUND unless you are a recipient). This is exactly the when/when-not/alternative guidance expected.

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