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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, yet the description adds real behavioral detail beyond them: the printed redirect URL is left untouched, a user confirmation step is required, and an optimistic-concurrency contract (expected_revision, conflict → re-read) governs retries. That is exactly the kind of context annotations cannot carry.

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, each carrying distinct payload (effect, precondition, concurrency protocol), with the core behavior front-loaded. No filler or restatement of the tool name.

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 mutating tool with no output schema and zero schema coverage, the description covers the risky parts: URL invariance, user confirmation, and revision/conflict handling. It does not say what destination formats are accepted or whether unrelated destination fields are reset, which is a minor residual gap.

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 0%, so the description must compensate, and it does partially: expected_revision is explained as coming from get_qr_code with defined conflict semantics. However, id and destination get no semantic treatment beyond their names, leaving two of three parameters undocumented.

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 (change an owned QR destination) and adds a distinguishing effect: the printed redirect URL is preserved, which separates it from create_qr or set_routing. It names get_qr_code only as a revision source rather than as an alternative, so sibling differentiation is implicit rather than explicit.

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 concrete operational context: confirm the intended destination with the user, supply expected_revision from get_qr_code, and re-read on conflict before retrying. It does not state when not to use this tool or which sibling handles related edits (e.g., set_routing), so it stops short of a full when/when-not treatment.

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