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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint, but the description adds a genuine error contract: it never raises a protocol error and instead returns {"error": ...} with fix guidance, and retry after correcting input is safe. That is real behavioral disclosure beyond the annotations, though failure modes for malformed optional fields (term/content) are not spelled out.

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?

Purpose is front-loaded in the first line, and usage/exclusions follow before the error contract. The inline JSON examples are somewhat verbose and split awkwardly across lines, but each sentence carries actionable 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?

With an output schema present, return values need no explanation, and the description still supplies the error shape, retry safety, usage boundaries and a concrete example. An agent has everything needed to call this correctly on the first attempt.

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% and each field already documents its utm_ mapping and defaults, so the baseline is 3. The worked input/output example adds modest value by showing how the four required params assemble into the final tagged_url, but it restates rather than extends the schema (optional term/content are absent from the example).

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 ('Build a UTM-tagged URL for campaign tracking') plus an explicit scope limit ('one tagged tracking URL'). It also names what it is not for ('analyzing campaign results') and points at the sibling audit_copy, so an agent can separate it from the rest of the toolset without opening the schema.

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 both a positive trigger ('Use to build one tagged tracking URL') and explicit exclusions, routing message-body work to audit_copy by name. The one-URL-at-a-time constraint is stated, which prevents batch misuse.

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