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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds value beyond them: per-row billing, that limit caps both rows and cost, the exact returned columns, and an untrusted-input warning for user-generated content. This is unusually rich behavioral disclosure.

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 core action and matching semantics, then usage routing, then return/billing details. Four compact sentences and a clause; nothing is redundant with the schema.

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 two-parameter search tool with no output schema, the description supplies the result columns, the cost model, and the input-trust caveat, which is everything an agent needs to call and interpret it correctly.

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 both parameters are documented in the schema; baseline would be 3. The description goes beyond it by tying limit to cost ('caps both rows and cost') and confirming the case-insensitive substring nature of query, which the schema does not state.

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 (search TikTok accounts) plus the matching semantics (case-insensitive substring on handle or display name) and ordering (by follower count). It is immediately distinguishable from get_tt_user_by_username (exact handle) and get_top_tt_users (no query) without opening any 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 states when to use it ('when you only know part of a name') and routes to three named alternatives for the neighboring cases, including the cross-platform one (search_users for Instagram). No ambiguity about which sibling to pick.

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