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

Annotations already declare the safety profile (readOnly=false, idempotent=true, destructive=false), and the description adds genuinely non-obvious consequences: destination changes propagate to postcards already in the mail stream, and color changes only reach templates at send time. It leaves unstated whether a partial update preserves untouched fields or whether the old destination link is retired.

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 short sentences, zero filler, with the core operations front-loaded and the side-effect caveats following. Every sentence contributes a distinct piece of information.

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?

A 5-parameter mutation tool with no output schema and full schema coverage needs mostly the propagation semantics, which the description supplies. The remaining gap is whether only supplied fields are changed (partial update), which an agent might want confirmed before calling.

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 schema already carries field formats and examples; the description adds semantic weight by clarifying that the destination is retroactive and that colors take effect at send time. It does not add anything about qr_code_id beyond what the schema states.

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?

Three specific verb+resource pairs ('rename a QR code', 'change where scans go', 'change its colors') immediately tell an agent exactly which fields this tool mutates. The QR-code focus separates it cleanly from the many sibling update/preview/delete template tools and from spur_create_qr_code.

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 rather than stated: this edits an existing code, and the note that a new destination affects already-mailed postcards implies 'use when you want retroactive changes'. There is no explicit when-not guidance or reference to alternatives such as spur_create_qr_code vs spur_delete_qr_code.

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