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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior, so the bar is lower, yet the description still adds a concrete operational constraint: poll no more than once a minute. It also discloses the incremental-read pattern (cursor from prior call), which is real behavior beyond the annotations.

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?

Four short sentences, front-loaded with purpose, then invocation, then polling pattern, then rate limit. No filler and no repetition of schema or annotation 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?

With no output schema, the description does useful work by revealing that the response yields a next_after cursor, and it covers prerequisites and rate limits for a 3-parameter tool. It stops short of describing the shape of returned messages, which would fully close the gap.

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 baseline is 3, but the description adds provenance the schema doesn't state: conversation_id and access_token come from contact_owner. Most valuably, it names next_after as the source of the "after" value — a field absent from the schema and, with no output schema, otherwise undiscoverable.

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?

The description opens with a concrete verb+resource ("Read messages in a conversation") and scopes it to conversations created by contact_owner, so the agent can place it in the workflow. It doesn't explicitly contrast itself with send_followup or other siblings, but the read-vs-create distinction is implicit and clear.

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?

It tells the agent exactly how to invoke it (pass the saved id and access_token), how to poll incrementally (use next_after from the last call as "after"), and imposes a rate limit of one poll per minute. What it lacks is an explicit when-not/exclusion clause naming an alternative tool for other cases.

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