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

Goes meaningfully beyond the annotations: attribution to the caller's seat, immutability, append-at-new-sequence semantics, required write scope, and the non-idempotent append behavior (which reinforces idempotentHint=false rather than contradicting it). It doesn't cover failure modes or response shape, but for a mutation tool with annotations present this is solid added context.

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?

Front-loaded with purpose, then consumers, then constraints, then scope/permissions, then the non-idempotency warning. Four dense sentences with no filler — each one carries information an agent would otherwise have to infer.

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?

Covers the full decision surface for a write tool: what it does, who reads the result, citation validity, campaign scoping, required scope, immutability, and append-on-each-call. With no output schema and only thin annotations, the description carries the burden and does so adequately; sealed-Space encryption is already handled in the schema.

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 coverage is 100%, so baseline is 3; the description earns above that by imposing a validity rule on citations ("must be pointers that resolve (A12, seq/340, paper/<id>)") that the schema only loosely implies, and by stating the campaign_id default. It adds no detail on from_seq/to_seq beyond the schema's inclusive-range text.

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?

Specific verb + resource ("Record your summary of a span of Space activity") with the write/read split made explicit by naming read_summaries and catch_me_up as the consumption path. An agent can distinguish this from the sibling readers without opening a schema.

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?

Gives a concrete trigger ("before going idle or handing off") and explains the downstream payoff (later arrivals catch up without replaying messages), which tells the agent when posting is worth it. It stops short of an explicit exclusion — e.g. "for direct messages use send_message instead" — so it's clear context rather than full when/when-not guidance.

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