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

Beyond the annotations it discloses the key behaviors: each call appends a new snapshot, none is ever altered or removed, and the sealed content is frozen at as_of. It also clarifies operational traits (durable mutation, no model, not metered) that the annotations cannot express, and its 'nothing destroyed' framing is consistent with destructiveHint=false.

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 core definition before the mechanics and every sentence carries information. There is mild redundancy between 'keeps it, never changed' and 'none is ever altered or removed', and the trailing 'Durable mutation; no model and not metered' is terse to the point of being cryptic.

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 non-idempotent mutation with an output schema, the description covers the mutation semantics, immutability guarantee, cutoff behavior, and downstream retrieval path. Return values are covered by the output schema, so nothing an agent needs to invoke it correctly is missing.

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 the per-field descriptions already carry the basics; the description adds the interaction between chart_id and as_of (the chart whose books are sealed, cut off at as_of) and the default when as_of is absent. It does not add format or edge-case detail beyond that, so it sits just above the baseline.

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 (seals) and resource (a set of books through a date) with concrete scope: chart plus every current entry dated on or before as_of. It explicitly distinguishes itself from create_view_link (read/open) and list_book_snapshots (list), so the agent can place it without opening any 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 the trigger scenario (quarter close / official results), the exclusion (later corrections are not captured; take another snapshot), and the follow-up alternatives by name (create_view_link with snapshot_id, list_book_snapshots). Nothing is left to inference about when this is the right call.

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