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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds genuine value beyond that by enumerating the returned field groups (name, company, phones, email, address, workflow status, lead source, sales rep, custom fields), which matters because there is no output schema. It does not mention auth scope, rate limits, or missing-record behavior.

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?

Front-loaded with the action and the returned payload in a single tight sentence; the trailing 'JobNimbus: GET /contacts/{jnid}' is a minor redundancy that adds little for an agent already holding the tool, but costs nothing materially.

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 read tool with no output schema, the description compensates well by naming the returned fields and confirming read-only semantics via annotations. Nothing an agent needs to invoke it correctly is missing, though error/empty-result behavior is unstated.

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?

There is a single parameter with 100% schema coverage, and the schema already defines jnid as the JobNimbus record id. The description only restates 'by jnid' with no added format or lookup guidance, so the baseline 3 applies.

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 ('Fetch a single contact by jnid') and enumerates the fields returned, which clearly separates it from the list_contacts sibling by operating on one record. It stops short of naming the alternative explicitly, but the 'single' scope makes the intent unambiguous.

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?

Usage is implied by the required jnid and the singular scope: you call this when you already have a contact id and need the full record. No when-not condition or direct routing to jobnimbus_list_contacts / jobnimbus_update_contact is stated.

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