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

Annotations already declare the mutation profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false), so the safety bar is lowered. The description contributes the genuine 'exactly one sentence' constraint, but says nothing about how the sentence is appended, ordering, or author attribution.

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?

A single sentence, front-loaded with the verb and the payload constraint, with zero filler. Nothing could be removed without losing information.

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?

With an output schema present, return values need no explanation, and annotations cover the mutation safety profile. The definition is nearly complete for a simple append tool, though it omits turn/ordering context that a relay game might require.

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 'exactly one sentence' phrasing reinforces the sentence parameter's cardinality limit, but adds no syntax or format detail beyond what the schema already documents for sentence and api_key.

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 (add) and resource (one sentence continuing the relay story), which is concrete enough to separate it from the read-side sibling relay_read. It does not explicitly name or contrast with that sibling, so it falls short of the top band.

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?

The description only states what the tool does; it gives no when-to-use context, no prerequisites, and no mention of the alternative relay_read for retrieving the story. An agent must infer the collaborative-turn usage entirely from the tool name.

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