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

Annotations already declare this is a non-destructive, non-open-world write, so the safety profile is covered. The description adds real behavioral context beyond that: the entry is created in the topic's unit (implying unit mismatch is a failure mode) and the call returns today's running total, which sets response expectations.

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?

Four short sentences with the core action front-loaded before the prerequisites, and each directive earns its place. Slight redundancy in "reports today's total" against the existing output schema keeps it from a 5.

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 a one-required-parameter write with a complete schema, an output schema, and annotations covering safety, the description supplies the remaining decision-relevant facts: the prerequisite lookup, the unit-conversion constraint, and the backdating field. Nothing an agent needs to invoke it correctly is missing.

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% and the schema already documents value/unit conversion, occurredAt timezone handling, and topicId sourcing, so the description is largely restating structured data. Its only marginal addition is tying value conversion to the topic resource, which does not exceed the schema's own example.

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?

Uses a specific verb and resource ("Records one entry on a topic") and adds the immediate effect ("reports today's total"), so the agent knows this is a single-entry write with a summary response. However, it never distinguishes itself from the sibling log_entries, which an agent could easily confuse with this tool.

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 operational guidance: convert the value to the topic's unit first, use occurredAt for backdated entries, and call list_topics first if the topicId is unknown. It lacks any explicit exclusion or comparison against the sibling log_entries, so the when-not-to-use this tool case is left to inference.

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