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

Annotations only cover safety flags (non-read-only, non-destructive), which the description cannot improve on. The description adds real behavioral context beyond them: per-workspace name uniqueness and the possibility of a `needs_confirmation` response, which warns the agent that creation may not complete in one call.

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?

Four compact sentences, front-loaded with the definition of a metric, then the constraint, then the trigger, then the caveat. No wasted prose, though the 'offer this' instruction is arguably guidance rather than description.

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 an 8-parameter write tool with no output schema, the description covers the key operational facts an agent needs: uniqueness, confirmation behavior, and the user-intent trigger. It does not explain the approvalId parameter or what a successful response returns, leaving minor gaps.

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 88%, so the schema already documents name, icon, unit, level, drives, workspace, and description in detail. The description only reinforces the name-uniqueness constraint and adds no syntax or format guidance beyond the schema, so the baseline 3 applies.

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 ('Create a metric — a number the workspace watches') with concrete examples (triage time, weekly signups, cost per run). This clearly separates it from ledger_metrics_update, ledger_metrics_list, and ledger_metrics_archive in the sibling set.

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 says to check ledger_metrics_list first and why (names are unique per workspace), and gives a trigger condition ('When a user says they want to track or measure something, offer this'). Both the prerequisite and the invocation context are stated.

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