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

Annotations already declare readOnlyHint=false, openWorldHint=true, and destructiveHint=true, so the safety profile is covered structurally. The description adds useful context (active vs scheduled output, mirroring POST /api/v1/streams/{stream}/destinations) but does not mention auth requirements, side effects on an existing stream, or what happens alongside remove_destination.

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?

Three tightly packed sentences that front-load the core action and then the required fields and endpoint mapping. Dense but no filler; the key-format clause is long yet earns its place by disambiguating platform-specific input.

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 7 parameters, no output schema, and annotations already covering safety, the description covers the action, the required fields, and the non-obvious key formats. Minor gaps remain around optional params (status, url, include_in_schedule), but the schema documents those adequately.

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 real value beyond the schema: the stream key format rules per platform (custom/instagram/rumble use rtmp:// or rtmps://, customsrt uses srt://) and the max-100 name constraint, which the schema does not encode. This is meaningful semantic enrichment.

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 ('Add a multistream destination to a stream') and clarifies the scope as multistream output to an external platform. This cleanly separates it from list_destinations, update_destination, and remove_destination without needing to name them.

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?

The description explains what the destination does ('enable active or scheduled output to an external platform'), which implies when it applies, but gives no explicit when-to-use/when-not guidance or routing to siblings like update_destination or list_destinations. Usage is inferable but not stated.

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