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

Annotations already declare a non-read-only, non-idempotent, open-world write, so the bar is lower, yet the description adds substantial context: continuous recognition behavior, default callback timing (after each song ends), the callbacks="before" mode and its lack of play length, plus the uniqueness and plan-slot constraints. This is real operational detail an agent cannot get 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?

The usage directive is front-loaded and the sentences largely earn their place. Slight redundancy in restating radio_id's uniqueness, which the schema already carries, keeps it from a 5.

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 mutation tool with an output schema (so return values need not be described), the description covers purpose, trigger condition, callback semantics, and a plan-slot prerequisite. It omits what happens on a duplicate radio_id and any auth/rate-limit notes, but nothing critical 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 the baseline is 3, and the schema already documents url, radio_id, and the callbacks enum. The description adds value beyond it by explaining that callbacks="before" results "have no play length" and re-emphasizing the account-unique constraint on radio_id.

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+resource ("Add a stream") and scopes it precisely to "continuous recognition" of a radio/live stream. The word "continuously" cleanly separates it from the one-off sibling recognize_song_from_url, so an agent can route without opening 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?

"Use this only when the user asks to start monitoring a radio or live stream" is an explicit when-to-use directive with an implicit exclusion of single-song recognition. It also names a precondition ("The account's streams plan needs a free stream slot"), though it never explicitly names a sibling alternative for one-off lookups.

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