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

With no annotations, the description carries the full burden. It usefully discloses a real behavioral quirk ('a bare psi is treated as psig') and a certification precondition (EPA 608/A2L). It does not say what happens if from_unit and to_unit cross families (e.g., psig to F), what precision/rounding is applied, or how invalid units are handled.

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 short sentences with the core conversion scope front-loaded, followed by the psi edge case and then the audience constraint. No filler, though the certification sentence is arguably a policy note rather than tool behavior.

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 3-required-param tool with no annotations and no output schema, the description covers supported units and one parsing edge case but leaves open the output shape (scalar vs object), cross-family conversion behavior, and failure modes. Adequate but with visible gaps for a tool an agent must call blind.

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 0% for all three parameters, so the description must compensate. It enumerates valid unit strings for from_unit/to_unit, which is genuinely valuable, and clarifies psi/psig ambiguity. It says nothing about the 'value' parameter's semantics (e.g., gauge vs absolute reference) or whether mixed-family conversions are legal input.

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+resource (convert between pressure and temperature units) and enumerates the supported unit set (psig, psia, kpa, bar, F, C), which makes the tool's scope immediately clear. It does not distinguish itself from siblings like pt_lookup or pt_reverse, which also deal with pressure and temperature relationships, so an agent must infer the boundary.

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?

There is no statement of when to use this versus pt_lookup/pt_reverse, which is the key routing question in this toolset (unit conversion vs refrigerant PT-based conversion). The only contextual guidance is an audience restriction ('for certified HVAC technicians'), which is not usage guidance about the tool's role.

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