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

Annotations already declare idempotentHint=true and destructiveHint=false, covering the safety profile. The description adds meaningful PATCH semantics ('only provided fields change'), which tells the agent that omitted fields are preserved – a non-obvious behavioral trait. It omits permission requirements and error behavior.

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?

Two short sentences, front-loaded with the core action and the key partial-update constraint, plus the underlying endpoint. Nothing is wasted.

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 and full schema coverage, the description is nearly complete for a partial-update mutation. It covers the partial-update contract and safety annotations carry idempotency; only edge cases like null handling (e.g., clearing url) and error behavior are unaddressed.

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 all 8 parameters are already documented in the schema with types and constraints. The description adds no per-parameter detail beyond the general 'only provided fields change' rule, so the baseline of 3 applies.

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 ('partially update') and resource ('multistream destination'), and clarifies the PATCH semantics that only provided fields change. It implicitly distinguishes itself from the add_destination/remove_destination siblings, though it doesn't name them explicitly.

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?

Usage is implied by the verb – use this to modify an existing destination rather than add or remove one – but there is no explicit when-to-use guidance, prerequisites, or named alternative among the many siblings. Adequate but with clear gaps.

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