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

The trailing 'Read-only' merely restates the readOnlyHint annotation and adds nothing. Useful beyond the annotations is the disclosure of what comes back (fact text, section, note ID, slug, page, license), which tells the agent the response is self-contained metadata rather than just a string.

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, zero filler, with the identifying action and ID format front-loaded before the return-value summary. Nothing is 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?

There is no output schema, and the description compensates by enumerating the returned fields, so the agent knows what to expect from a call. For a single-parameter read tool this is nearly complete; only error behavior for an invalid or stale fact ID 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 0%, so the description must carry the burden, and it does: it names the parameter's meaning ('permanent fact ID'), gives the literal format prefix 'iil:fact:', and states its provenance. It does not mention the 40-character limit or behavior on malformed/unknown IDs.

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 ('Look up one fact') plus the identifier namespace ('iil:fact:...'), which distinguishes it from note-level siblings like read_note. The reference to 'ask sources' signals the upstream tool that produces these IDs, though it never explicitly contrasts itself with read_note.

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?

Explains where the required ID comes from ('as returned in ask sources'), which effectively tells the agent this is a follow-up call after ask. It gives no explicit when-not-to-use guidance or named alternative for retrieving whole notes.

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