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

Annotations already declare a non-destructive, idempotent write, and the description adds genuine scope context beyond them: the update is bounded to 'messages through the supplied message sequence' and explicitly does not acknowledge or complete work. It still omits auth requirements and error/return behavior, but the added scoping is real value.

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, front-loaded sentences with no filler; the core action leads and the constraints follow. Efficient, though the second and third sentences could be tightened.

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, non-destructive idempotent write with 3 params and no output schema, the description covers action, scope, and exclusions adequately. The main remaining gap is parameter-level detail, which the schema itself only partially supplies.

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 only 33% – 'connection' is documented but channel_id and through_seq are not. The description partially compensates by clarifying that marking happens 'in one accessible channel' and 'through the supplied message sequence', which maps to those two params, but it adds no format or boundary detail beyond that.

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+resource ('Record read progress') scoped to an authorized agent and a single channel, which is clear enough to act on. It does not explicitly differentiate itself from nearby siblings like tincan_open, tincan_snapshot, or tincan_mentions_search, so it falls short of a 5.

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?

The negative scoping ('Does not acknowledge or complete agent work') implicitly steers the agent away from task-completion tools like a2a_task_update, but no alternative is named and no explicit when-to-use condition is given. Usage is implied rather than stated.

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