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

Annotations already declare readOnly/openWorld/non-destructive, and the description adds real behavior on top: profile_posts exposes only the most recent public posts, post includes replies and the author's own continuation posts (threadItems), list actions return { results, next_cursor, next }, and no action ever accepts a cursor because Threads serves no further pages. Those are exactly the operational facts an agent cannot infer from 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?

Front-loaded with the platform and the action/argument pattern, then one clause per action, then a closing note on return shapes and pagination. Every sentence carries information; nothing is restated from the title or annotations.

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 six-parameter, enum-dispatched tool with no output schema, the description covers all actions, their arguments, the return shape for both list and single-item actions, and the pagination limitation. An agent has everything needed to select an action and interpret the response.

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 100%, so the baseline is 3, but the description adds value the schema cannot express: it maps each parameter to the action(s) that accept it (query to search/search_users, start_date/end_date to search only, username to profile/profile_posts, id to post). That conditional binding is genuinely useful, though the individual formats are left to the schema.

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 ('Read public Threads data') and enumerates all five actions with the resource each one targets. It is immediately distinguishable from siblings such as instagram, facebook, and reddit because the platform and the exact action set are named.

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?

Each action is annotated with the argument it takes and the shape of what it returns, so an agent can pick search vs search_users vs profile vs profile_posts vs post without opening the schema. It stops short of any tool-level exclusion or alternative routing (e.g., when to prefer instagram or web-search instead), so it is strong context but not a full when/when-not guide.

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