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

With no annotations, the description carries the full load and mostly succeeds: it discloses the state effect (extends life), the one-per-session limit, the ownership/sunk restrictions, and that skips are attributed as AI in origin. It omits what happens on failure (e.g., skipping an invalid or already-sunk id) and how much 'a little' actually is.

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-loads the definition and effect before the constraints, and every sentence carries a rule. Slight redundancy between the first sentence's 'worth reading' framing and the second sentence's restatement of the same criterion.

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 no-annotation, no-output-schema mutation tool the key constraints are all present, letting an agent call it correctly. It would be stronger with concrete return/error behavior and a clearer sibling comparison against cast_thought.

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?

Only one parameter and schema coverage is 100%, so the schema already documents 'id' with the same 'pebble id from read_river' note. The description adds no syntax or format 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?

Defines the metaphor precisely ('Skipping a pebble means this was worth reading') and states the concrete effect: it extends that pebble's life. It also implicitly separates the tool from cast_thought by forbidding self-skips, though it never names the sibling directly.

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?

Explicit when-to-use ('only for thoughts you genuinely found worth reading', 'use it sparingly'), explicit when-not ('you cannot skip your own casts or pebbles that have already sunk'), a rate constraint ('one skip per pebble per session'), and a routing hint for inputs ('get ids from read_river').

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