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

The description reveals a non-obvious runtime behavior: 'the printed code keeps working' after destination changes, which is valuable beyond the idempotent/destructive annotations. It also notes the dynamic-code-only restriction for destination fields. No contradiction with 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?

A single information-dense sentence with no filler; the key instruction 'Send only what changes' is included after the field list. Every phrase earns its place.

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 12-parameter update tool with a low-coverage schema, the description covers the most important caveats (dynamic-only, partial update, printed-code behavior) but leaves exact field groupings and value formats (colors, frame styles, domain_id semantics) unspecified. Annotations and output schema fill some gaps, but not all.

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?

With only 25% schema coverage, the description adds meaning by explaining slug as 'link name on the account's domain', expires_at as 'ISO or null', and destination fields as dynamic-code-only. However, 'colors, frame' is a loose mapping to bg_color/fg_color/frame_style/frame_caption and does not specify allowed values, so it only partially compensates for the schema gap.

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 identifies a specific operation—'Change a QR code'—and enumerates the updatable fields, so an agent can tell it apart from create/delete/list siblings without opening the schema. It does not explicitly name siblings or state 'existing code', but the verb and 'Send only what changes' make the update semantics unmistakable.

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?

'Send only what changes' gives a clear partial-update usage rule, and 'dynamic codes only; the printed code keeps working' provides an explicit when/where constraint for destination changes. It does not describe scenarios where create_qr_code would be preferred, but the context is sufficient for an agent to avoid misusing it.

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