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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a non-obvious behavioral trait beyond the annotations: logged-out search lacks sort/cursor and pagination is limited, so the agent should check pagination_limited. Useful, though brief.

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 dense sentences, front-loaded with the core action, followed by parameter sourcing and routing guidance. No filler; every clause earns its place.

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 needn't be explained, and the description still flags the pagination limitation. For a 2-param read tool with full annotation and schema coverage, nothing an agent needs to invoke it correctly is missing.

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 both parameters are already documented. The description restates that q is the canonical name/search_query and tag_id comes from threads_profile_topics or a post topic, which largely duplicates the schema and adds little new syntax or format detail. Baseline 3.

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+scope: 'Search public Threads posts for one topic tag.' The 'one topic tag' scope clearly distinguishes it from threads_search (text queries) and threads_profile_posts (profile feeds) without needing the schema.

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?

Explicitly routes the agent: use threads_search for text queries, threads_profile_topics to discover tags, and threads_profile_posts for profile feeds. It also tells the agent where q and tag_id come from, so both when-to-use and prerequisites are covered.

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