mark_read

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

With no annotations, this description carries the burden well: it discloses a permission-style constraint (refusal for other roles) and a non-obvious side effect (the unread counter decrement) that an agent could not infer otherwise. It does not cover idempotency or partial-failure behavior when a batch contains mixed-role messages.

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?

Three short sentences, each earning its place: purpose, constraint, and differentiating side effect. The unread-counter fact is front-loadable but stays tight and is not buried.

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 two-parameter mutation with an output schema present, the description covers purpose, access constraint, and the key side effect, so nothing essential is missing. Minor gaps remain around behavior with no arguments and batch error semantics.

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 0%, so the description must compensate, and it does: it explains that message_id targets a single message while message_ids targets several, mapping the two parameters to their distinct use cases. It does not explicitly state that supplying both or neither is invalid, leaving some ambiguity.

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 (one message via message_id or several via message_ids) with an explicit scope restriction ('addressed to you'). It also names the sibling read_inbox and explains how this tool differs from it, so the agent can distinguish the two 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?

Gives clear selection context: use this when you need messages actually marked read, since it is 'the ONLY thing that decrements the unread counter — read_inbox does not.' It also states the exclusion (refuses messages addressed to a different role). It stops short of spelling out when read_inbox is the better choice, but the routing signal is strong.

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