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

Beyond the annotations (idempotentHint=true, readOnlyHint=false), the description discloses specific behaviors: 'One reaction per receipt; identical retries reuse it and conflicting changes return 409.' It also adds caveats about proving AI identity and security guidance ('Never publish the receipt'). This is rich behavioral context that annotations alone don't provide.

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?

The description is a compact paragraph with every sentence contributing: purpose, retry semantics, conflict behavior, not_found handling, identity caveat, and security warning. It's front-loaded with the core action and efficiently packs important constraints without fluff.

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?

The description covers the tool's purpose, usage context, behavioral edge cases, security, and parameter relationships. Given that an output schema exists and annotations handle safety flags, nothing essential is missing for an agent to call it correctly.

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?

The schema already covers 75% of parameters with detailed descriptions (receipt security, status enum, test_run, public_topic). The description adds context about the receipt's origin and usage ('Use its private optional_reaction.receipt and one status') and reinforces the security constraint. This meaningfully supplements the schema, so it earns above the baseline.

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?

The description clearly states the tool's purpose: 'Optional self-reported reaction to a successful read, including an empty result.' This distinguishes it from siblings like read_workspace (the read itself) and write_note (a note, not a reaction). The title reinforces the action and scope.

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 explains when to use it (after a read, optionally) and notes that 'Reading stays free without this call,' implying it's not required. It also describes retry behavior and conflict handling. However, it doesn't explicitly contrast with write_note or state when not to use it beyond the optionality, so it's clear but lacks explicit exclusions.

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