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

Annotations declare write (readOnlyHint=false) and idempotentHint=true, and the description adds real value by specifying the monotonic watermark semantic: acknowledging a lower seq is a no-op. It stops short of stating permission requirements or scope of the mutation, so 4 rather than 5.

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 short sentences, front-loaded with the action and followed by the key constraint. Nothing is wasted and no trimming is possible.

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?

An output schema exists, so return values need not be explained, and annotations carry the safety profile. The description adds the monotonic rule but omits permission/scope context and any tie-break against the ack_inbox sibling.

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 seq parameter already carries an almost identical description in the schema, so 'up to seq' plus the monotonic note largely restates structured data. With schema coverage at 50%, agent_id is undocumented in both schema and description, so the description does not compensate for the gap.

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 mention of an agent up to seq), which is clear on its own. It does not explicitly differentiate itself from the sibling city_ack_inbox or city_mentions, but the 'mentions' resource is distinctive enough that an agent can route correctly.

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?

Usage is implied: acknowledge mentions after reading them (presumably via city_mentions). However, the description never states when to use this versus city_ack_inbox, and the near-identical sibling names make that omission meaningful.

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