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

Adds substantial context beyond the annotations: a per-device rate limit (one message per 30 s) that is shared with the device's own quota, plus the fact that everything written is public. These operational and privacy constraints are not derivable from readOnlyHint/idempotentHint/openWorldHint and materially affect caller behavior.

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?

Three tight sentences: identity of the operation first, then the motivating use cases, then the operational constraints. No restatement of the name or title and no filler.

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?

Covers what it writes, where, rate limits, and visibility for a 2-parameter tool with a nested metrics object. The only gap is the response shape (no output schema exists), though "exactly as POST /add/{device} would" partially compensates.

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% – device naming rules and the flat metrics object (1-10 numeric/short-string values) are already fully documented in the schema. The description adds no new syntax or format detail for either parameter, 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?

Opens with a specific verb+resource ("Store one reading for a device") and pins semantics by equating it to POST /add/{device}. This clearly positions it as the write counterpart to the read-oriented siblings (get_history, get_latest, wait_for_reading), so an agent can distinguish it without opening schemas.

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?

Gives concrete when-to-use context: testing a dashboard or integration before hardware exists, or writing to a channel a device listens to. It does not explicitly name an alternative sibling (e.g., wait_for_reading for pull-based flows) or state when-not-to-use, so it falls short of the top band.

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