Create or replace a named PyMOL selection from a selection expression, enabling reuse in later structure analysis.
Creates (or replaces) a named selection for later reuse.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | Identifier you'll refer to later (e.g. ``active_site``). | |
| selection | Yes | PyMOL selection expression to assign to that name. |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v1.5.1Input schema / properties / name / descriptionAdded value: +"Identifier you'll refer to later (e.g. ``active_site``)."Input schema / properties / selection / descriptionAdded value: +"PyMOL selection expression to assign to that name."v1.2.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the crucial replace-on-name-conflict semantics ('or replaces') that the annotations only hint at via idempotentHint, plus the persistence intent ('for later reuse'). It stops short of saying whether the stored selection is re-evaluated as the structure changes.
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?
A single front-loaded sentence with zero filler; the parenthetical replace clause is the most economical way to encode the overwrite 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?
With an output schema present and annotations covering safety and idempotency, the description need not explain return values. For a two-parameter selection tool it is nearly complete, with only the lack of sibling routing guidance keeping it from a 5 as the surrounding toolset is large and contains overlapping operations.
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%, with 'name' documented as an identifier with an example and 'selection' documented as a PyMOL selection expression, so the description has little left to add. 'named selection' and 'for later reuse' only loosely reinforce the schema and add no syntax or format detail.
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 names a specific verb ('Creates (or replaces)') and resource ('a named selection'), so the agent knows exactly what the tool produces. It does not explicitly distinguish itself from sibling tools like create, extract, or execute_pymol_command, which prevents a 5.
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?
'for later reuse' implies the intent (persisting a selection so other commands can reference it by name), but there is no explicit when-to-use vs when-not guidance and no mention of alternatives such as create or execute_pymol_command. Usage is inferable rather than stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.