Append a note to a card

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

Annotations declare readOnlyHint=false (mutation) and destructiveHint=false, which the description supports by explaining it appends rather than rewrites. The description adds value by explaining concurrency safety and the "created if it does not exist" section behavior via the schema. It doesn't mention idempotency implications or whether the timestamp is server-side, but annotations cover the core safety profile.

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, front-loaded with the core action, and zero filler. Every phrase earns its place — the timestamped-line detail, the cost comparison, and the concurrency safety are all high-value.

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 append-only tool with 4 params (100% schema coverage) and an output schema, the description plus schema fully covers the behavioral contract. The concurrency-safety note addresses the key risk of a mutation tool, and the heading-creation behavior is documented in the schema.

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%, so the baseline is 3. The description adds the "timestamped" behavior and the "safe for concurrent writes" framing but doesn't add details about parameter formats or constraints beyond schema descriptions, which already document actor defaulting and section creation.

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?

Description says "Append one timestamped line under a heading" — specific verb (append), specific resource (card), and specific mechanism (timestamped line under heading). It distinguishes from sibling card_write and card_patch by emphasizing the append-only, cheap, concurrent-safe nature.

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?

Description says it's "cheaper than rewriting the body and safe when two agents write at once," which signals when to prefer this tool over writing/patching the body. It doesn't explicitly name the alternative tools (card_write/card_patch) or give exclusions, but the context is clear enough to guide selection.

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