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

Annotations cover the safety profile (non-read-only, non-idempotent, non-destructive), and the description adds real behavioral context beyond them: this overwrites the value directly and does NOT create a check-in, so history is lost. It omits permissions/validation details, but for a simple field write this is solid.

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?

Two sentences, zero filler, with the core behavior ('only the current value', 'without creating a check-in') front-loaded before the alternative-tool routing.

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?

There is no output schema and no nested objects, so the description need not explain returns. It covers purpose, sibling routing, and the key side effect; only parameter format/validation detail is missing for a two-param mutation.

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 0%, so the description carries the full burden for two params. It implies keyResultId selects the target and currentValue is the new value, but gives no format, unit, range, or absolute-vs-delta guidance for the numeric value.

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), resource (key result value), and explicitly bounds the scope to 'only the current value' versus full updates. An agent can distinguish it from both update_key_result and create_check_in 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?

Names the alternative (create_check_in) and the exact condition that selects it (the user is describing progress), plus the reason (preserves narrative history). This is explicit when-to-use / when-not-to-use guidance rather than inferred.

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