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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the mutation/safety profile is covered structurally. The description adds one meaningful behavioral fact — the read state is scoped to the current viewer — but says nothing about who may mark a conversation read or what the effect on shared state is.

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?

A single short sentence that front-loads the action and qualifier with zero filler. It is well-sized for a simple toggle operation, though it is so terse that it offers little marginal content.

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 low-complexity, two-parameter toggle with a fully documented schema and annotations covering the safety profile, the description is close to sufficient. The per-viewer scoping note is the key behavioral detail; only error/auth behavior is left unspecified, which is minor here.

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 convoId and apiKey are already documented in the schema, and there are no enums or nested objects to clarify. The description adds no syntax or format detail beyond the structured fields, so the baseline of 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 and resource ("Mark a conversation as read") with the scope qualifier "for the current viewer." An agent can distinguish this from get_convo, update_convo, and add_convo_note by the verb. It stops short of naming a sibling to route against, so it lands at 4.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives such as update_convo for other conversation changes. The reader must infer the trigger condition (a viewer has unread messages) entirely from context.

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