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

Annotations already cover readOnly/idempotent/non-destructive, but the description adds material behavior the annotations cannot: per-row billing, that limit caps both rows and cost, the exact returned column set, and a security warning that results are user-generated untrusted content. This is well beyond annotation coverage.

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?

No filler sentences; scope, alternative routing, return shape, cost model, and safety warning are each delivered in one clause. Front-loaded with the core purpose before secondary details.

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 compensates by enumerating returned fields (pk, title, display_artist, duration_in_ms, is_explicit), the ordering, the cost model, and the untrusted-data caveat. An agent has everything needed to call and interpret it.

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 baseline is 3, but the description adds real meaning: limit is tied to cost/billing and caps rows, and query is characterized as case-insensitive substring matching over title or artist. It stops short of documenting edge cases like empty result behavior.

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 Instagram music tracks (audio used in reels)'), plus the match semantics (case-insensitive substring on title/artist) and sort order. It also explicitly names the downstream purpose (find a track pk) and distinguishes itself from get_track_by_id and get_top_tracks.

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?

Gives explicit when-to-use ('Use it to find a track pk') and names the alternative for a different need ('use get_track_by_id for full details'). The agent knows exactly which sibling to pick and why.

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