companies_select

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

Annotations declare readOnlyHint=false, idempotentHint=true and non-destructive but say nothing about scope or persistence; the description fills that gap by explaining the selection is session-scoped and changes the context of all subsequent company-scoped requests. Merge semantics versus a possible sibling are not covered.

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, front-loaded with the action and its effect, then the prerequisite. Nothing redundant.

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-parameter session-state tool with annotations and no output schema, the definition covers action, side effect, and prerequisite. The only meaningful omission is disambiguation from companies_set_active.

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 single parameter is fully documented, so the baseline is 3. The description adds value by naming the source of the UUID (companies_list), which the schema does not say.

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 ('Select the active company for the current session') and explains the concrete effect (sets the X-Company header for subsequent calls). It does not, however, distinguish itself from the very similar sibling companies_set_active, which an agent will see in the same namespace.

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 an explicit prerequisite sequence: call companies_list first to obtain available company UUIDs, then select one. That is real routing guidance, though it omits when to prefer this over companies_set_active.

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