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

With annotations already declaring destructiveHint=true, idempotentHint=true, and openWorldHint=true, the bar is lower, yet the description still adds real value: it clarifies that only provided fields change (partial PATCH, not full replace) and that certain live and lifecycle changes are rejected by the API. It stops short of saying what is destroyed or what permissions are needed, so it is not a 5.

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 tight sentences, front-loaded with the core PATCH semantics before the capability list and the API restriction. Slightly dense, but no sentence is wasted and the endpoint reference is placed last where it belongs.

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 an 8-parameter mutation tool with no output schema but full annotation coverage, the description supplies the key behavioral context an agent needs: partial-update behavior, side effects, and API-imposed restrictions. It omits any indication of the response shape or error behavior, which is the only notable hole.

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 every parameter is already documented in the schema and the baseline is 3. The description contributes only the general 'only provided fields change' rule plus a hint that 'name' can be synced from a connected platform; it adds no per-parameter meaning beyond the schema.

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 names a specific verb and resource ('Partially update a multistream destination') and even cites the underlying operation ('Mirrors PATCH /api/v1/streams/{stream}/destinations/{destination}'), which makes the read-modify semantics unambiguous. The word 'partially' implicitly separates it from add_destination and remove_destination, but no sibling is named outright.

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?

It lists what the tool can do ('overwrite settings, change scheduled output, pause a destination or sync a connected platform's title') but never states when to prefer this over add_destination, remove_destination, or update_stream. The note that live configuration and connected-destination lifecycle changes are API-restricted is a useful constraint, but it is a limitation rather than routing guidance.

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