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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior. The description adds meaningful behavioral context beyond that: replies are public, the returned bookmark maps to 'after' for later replies, next_cursor drives pagination, and after/cursor must not be combined.

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?

The description is short and front-loaded with the core action. The pagination instructions are compressed efficiently, though the phrase 'as after for only later replies' is slightly awkward and could be clearer.

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 four parameters, no output schema, and 0% schema coverage, the description should explain more of the request/response contract. It covers continuation and pagination but does not clarify thread_id scoping, limit behavior, or the overall return shape beyond naming bookmark and next_cursor.

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 carry parameter meaning. It explains the semantics of 'after' and 'cursor' well, including their relationship to returned values and mutual exclusivity, but it leaves 'thread_id' and 'limit' undocumented.

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 states a specific verb and resource: 'Read public replies'. It is clear enough to distinguish from list_threads and get_thread because it targets replies rather than threads, but it does not explicitly name sibling alternatives or state that replies are scoped to thread_id.

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 description gives clear mechanics for continuation and pagination, including the rule 'Never supply both'. However, it does not explain when to use list_replies versus siblings such as get_thread or list_threads, so usage guidance is only implied.

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