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

Annotations only say it is a non-idempotent, non-destructive write. The description adds substantive behavior: metric_key immediately re-baselines the goal rather than relabeling, at_risk is only ever set deliberately and never automatic, and current_value must not be set. That is real context beyond the structured fields.

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?

Front-loaded with the operation and its field list, then layered with targeted caveats. Dense but nearly every sentence carries a distinct constraint; the metric_key paragraph is slightly long relative to the rest but 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 15-parameter mutation with no output schema and no idempotency guarantee, the description covers the risky behaviors (re-baselining, at_risk semantics, current_value prohibition) well. It leaves response shape and the behavior of unmentioned fields implicit, but annotations and the full schema description coverage fill much of that 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 coverage is 100% so the baseline is 3, but the description adds meaning the schema lacks: why at_risk carries signal, that manual_done advances a manual goal, and the re-baselining consequence of metric_key. It does not explain every parameter (e.g. stage, priority, category), so it stops short of a 5.

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 (Update) and resource (a goal), enumerates the mutable fields (status, target, tags, metric, dates, manual counter), and positions itself against siblings like create_goal, delete_goal, refresh_goals, and goal_metrics. An agent can distinguish it from those siblings without opening any 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 explicit when-to-use guidance: pass manual_done to advance a manual goal, do not set current_value (refresh_goals re-reads measured goals), call goal_metrics first before setting metric_key, and use this instead of deleting/recreating to fix a wrong metric. Alternatives and exclusions are named.

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