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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds the master-API-key requirement, which is useful operational context beyond the annotations, but says nothing about rate limits, error behavior, or the fact that the title ('View or Update Deal') misleadingly suggests write capability.

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?

The core purpose and auth requirement are front-loaded in a single tight sentence, which is good. The pricing boilerplate that follows does not help an agent select or invoke the tool and is mildly noisy, but it is delimited and clearly ancillary.

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-by-ID tool with an output schema and full annotation coverage, the description supplies what the agent needs: what it fetches and the auth prerequisite. Return value details are correctly left to the output schema; only the routing vs. sibling tools is unaddressed.

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 100% with a single opportunity_id parameter, so the baseline of 3 applies. The phrase 'by ID' in the description adds no format, encoding, or sourcing detail beyond what the schema already documents.

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 states a specific verb and resource: 'View a deal (opportunity) by ID,' which maps cleanly to the get_apollo_opportunities_opportunity_id name. It does not explicitly distinguish itself from get_apollo_opportunities_search or get_apollo_opportunities_opportunity_id's update sibling, but the intent is 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?

It provides the prerequisite 'Requires a master API key,' which tells the agent an auth condition must be met before calling. However, it gives no guidance on when to use this single-record fetch vs. get_apollo_opportunities_search or when to use the patch sibling for updating.

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