rms_cur

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

Annotations already cover readOnly, idempotent, non-destructive, so the safety profile is set; the description nonetheless adds meaningful behavior beyond them by stating that this reports distance without reorienting coordinates and by declaring the precondition of matching atom counts. It stops short of describing failure behavior when atom counts mismatch or how the number is reported, so not a 5.

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 paragraphs, front-loaded with the definition, then routing, then the precondition. No filler, no restatement of the tool name, and each sentence carries distinct 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?

For a two-selection read-only metric tool with a full-coverage schema, rich annotations, and an output schema in place, nothing an agent needs to invoke it correctly is missing. The description covers what it computes, how it differs from alternatives, and its one hard precondition.

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 coverage is 100% and the schema already labels mobile and target with the same-atom-count constraint, so the description adds little per-parameter meaning. The one added nuance is that the count constraint is a hard requirement rather than a note, but it is a restatement of the schema text.

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 and resource ("Measures RMSD between two selections") plus the critical qualifier "*without* moving anything", which is exactly what separates it from align and super. An agent can identify this tool from the name-plus-description alone without comparing 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?

Explicitly names both conditions for use (structures already superposed; wanting current-position distance) and names three alternatives (align, super, superposition_view) with what each does differently and why one would pick it instead. This is the strongest kind of routing guidance.

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