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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description still adds real value beyond them: a concrete sunset ('12 months after the new tools launch'), notice history, and a migration doc URL. The GDPR/PECR paragraph is behavioral context too, but it is about email audience lawfulness rather than about what this call does, so it adds noise as much as signal.

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?

The critical information (deprecated, use list_field_sets, sunset window, migration link) is front-loaded, which is good. But the sentence about credits per record, the emailed-notice detail, and especially the UK GDPR Article 6(1)(f) / PECR corporate-subscriber paragraph are tangential to invoking this tool and dilute the message.

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 deprecated, zero-parameter, read-only tool with an output schema and full annotation coverage, nothing an agent needs is missing: replacement tool, sunset timing, and migration path are all stated. Return values need not be described because an output schema exists.

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?

There are zero parameters, so the baseline is 4. The schema description notes the old arguments are unchanged and mapped by an adapter to the new tools, and the description points to the migration doc for the mapping, which is adequate for an argument-less call.

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 ('lists the columns of one field bundle') and immediately flags the tool as deprecated. It also names the replacement sibling, so an agent can distinguish it from list_field_sets without inspecting either 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?

Explicitly routes the agent away ('Use list_field_sets instead') and explains what the alternative returns ('every field set with its exact columns and credits per record'). The only usage scenario is a legacy/compatibility call, which is implied by the deprecation framing.

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