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

Annotations already cover readOnlyHint, idempotentHint, and destructiveHint. The description adds behavioral value beyond those by revealing that the response is an 'opaque version' and that sensitive legal/identity content is omitted. This is useful context for the agent about the nature of the returned data.

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?

One tightly written sentence with no filler. The primary action is front-loaded, and the limitations follow immediately. Every part of the sentence earns its place.

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 simple two-ID read operation with a readOnly annotation and an output schema, the description is complete enough. It states what is returned, what is not returned, and the safe read-only nature is already annotated. An agent has sufficient information to select and invoke it correctly.

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 0%, and the description provides no parameter-level guidance. project_id and investment_id are fairly self-explanatory as identifiers, but the description does not clarify their relationship, scoping, or why both are required. With low schema coverage, the description carries the burden and does not compensate.

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 uses a specific verb and resource: 'Read safe investment milestones and an opaque version.' The negative clause 'no agreement bodies, signer identities or raw evidence' sharply distinguishes this from sibling tools like close_investment or list_investments. An agent can immediately tell what this tool does and what it deliberately excludes.

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?

The description makes the read-only inspection intent clear and explicitly tells the agent what will not be available, such as agreement bodies and signer identities. It does not name specific sibling alternatives like list_investments, but the content boundaries are strong enough to steer an agent away from this tool when those artifacts are needed.

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