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

No annotations are supplied, so the description carries the full disclosure burden, and it mostly doesn't: it does not say whether the operation mutates state, where pinned spans are stored, whether pinning is idempotent or conflicts on duplicate IDs, or what permissions are needed. 'classify + hash-pin' hints at internal processing but explains none of the observable behavior.

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?

It is a single compact line with the action front-loaded and a parenthetical for the mechanism, so it wastes no space. That brevity, however, edges into under-specification rather than efficiency.

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?

A three-parameter mutation-style tool with no annotations, no output schema, and zero schema coverage needs a far fuller description to be callable with confidence; the current text leaves storage, return behavior, and two parameters unexplained.

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% for three parameters. The description alludes to 'spans' and implicitly to classification, but never explains event_id, pinned_ids, or the expected string format of span entries, so two of three parameters remain fully undocumented.

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 verb 'pin' and object 'invariants ... spans' are present, but the phrasing is dense jargon and does not distinguish the tool from its sibling 'pin' (nor from 'audit'/'reinject'). An agent can guess it captures something before compaction, but cannot confidently separate it from the near-identically named alternative.

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 only usage cue is the temporal hint 'pre-compaction'. There is no statement of when to prefer this over pin, audit, or reinject, no prerequisites, and no exclusions — the agent must infer all routing from the name alone.

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