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

Annotations already carry the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=true), so the bar is lowered. The description adds the either/or selection rule between the two anchor parameters, which is useful behavioral context. It does not disclose what happens if both IDs are supplied, the default radius, or the shape of the returned context — but for a read-only fetch with strong annotation coverage, this is acceptable.

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 sentences with no filler: the first front-loads the purpose and endpoint, the second states the selection rule. Every word earns its place, and the most decision-relevant information (which anchor to use) comes immediately after the purpose.

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?

With no output schema and five parameters, the description covers the core call flow (anchor selection and radius) but omits edge behavior — what happens if both anchor IDs are passed, the default radius when omitted, and what the returned context actually contains. Annotations cover safety, so the remaining gaps are moderate rather than critical for a simple read operation.

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 only 20%, so the description carries meaningful weight. It adds semantics for three key parameters: aroundStanzaId/aroundMessageId (the either/or anchor choice) and radius (count of messages before/after). However, appId's B2B-mode requirement is left to the schema, and chatId gets no added context beyond the schema. The description partially compensates for the low coverage but not fully.

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-resource pair ('Fetch the messages surrounding a target message') and includes the exact endpoint path. The purpose is clearly distinct from siblings like ethora-messages-search-v2 (search) and ethora-chats-history-v2 (history), though it doesn't explicitly name those alternatives to draw the contrast.

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 gives invocation guidance — 'Provide either aroundStanzaId or aroundMessageId; radius controls how many messages before/after' — which tells the agent how to select parameters. However, it does not state when to prefer this tool over the sibling message/history/search tools, nor does it mention prerequisites like the app-select or B2B mode noted in the schema.

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