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

Annotations already declare readOnlyHint=true, and the description's 'read-only compatibility tool' largely restates that rather than adding new disclosure. It does add useful context about the return payload (full text plus metadata for citation), but says nothing about behavior for missing/invalid IDs or whether any auth is required.

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?

Two tight sentences with the action and the prerequisite front-loaded and no filler. The phrase 'compatibility tool' is unexplained jargon that slightly muddies an otherwise clean statement.

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 single-parameter read tool with full schema coverage and no output schema, the description covers the action, the precondition, and the shape of the result. The only real gap is error/not-found behavior, which is minor at this complexity.

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 and schema description coverage is 100%, with the schema itself explaining that the ID comes from the search tool. The description repeats 'by ID' but adds no format or sourcing detail beyond the schema, 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 one Open Brain thought by ID') plus what it returns ('full text and metadata for citation'). The 'after using search' framing implicitly separates it from search_thoughts/list_thoughts, which only locate records rather than returning full text.

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?

'Fetch ... after using search' gives a clear sequencing rule and 'for citation' names the use case, so an agent knows to reach for this after a search returns an ID. It doesn't state explicit exclusions (e.g., when to use list_thoughts instead of fetching by ID), so it stops short of the top mark.

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